Add authoritative fighter surface state

Reviewed-on: #58
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

.gitea/workflows/ci.yml

@@ -129,8 +129,11 @@ jobs:
             libusb-1.0-0-dev \
             libwayland-dev \
             libx11-dev \
+            libxfixes3 \
+            libxi6 \
             libxkbcommon-dev \
             libxkbcommon-x11-0 \
+            blender \
             lld-19 \
             llvm-19 \
             mesa-vulkan-drivers \
@@ -141,9 +144,39 @@ jobs:
           echo "/usr/lib/llvm-19/bin" >> "$GITHUB_PATH"
           rm -f "$HOME/.cache/cargo-xwin/clang-cl"
 
+      - name: Install pinned Blender
+        run: |
+          scripts/install-blender.sh "$RUNNER_TEMP/blender"
+          echo "BLENDER=$RUNNER_TEMP/blender/blender" >> "$GITHUB_ENV"
+
       - name: Preprocess assets
         run: cargo run --locked --bin process-assets --no-default-features --features debug_features -j 4
 
+      - name: Verify processed battlefield asset
+        run: |
+          python3 - <<'PY'
+          import json
+          import struct
+
+          path = "imported_assets/Default/stages/battlefield/bf2.blend"
+          with open(path, "rb") as asset:
+              header = asset.read(12)
+              if len(header) != 12:
+                  raise SystemExit(f"processed asset is truncated: {path}")
+              magic, version, length = struct.unpack("<4sII", header)
+              if magic != b"glTF" or version != 2 or length != asset.seek(0, 2):
+                  raise SystemExit(f"processed asset is not a valid GLB: {path}")
+              asset.seek(12)
+              json_length, chunk_type = struct.unpack("<II", asset.read(8))
+              if chunk_type != 0x4E4F534A:
+                  raise SystemExit(f"processed asset has no JSON chunk: {path}")
+              document = json.loads(asset.read(json_length))
+          meshes = document.get("meshes", [])
+          if not meshes:
+              raise SystemExit(f"processed asset contains no meshes: {path}")
+          print(f"{path}: {len(meshes)} meshes, {length} bytes")
+          PY
+
       - name: Build production binary
         run: cargo build --locked --profile production --no-default-features --features debug_features -j 4
 

Cargo.toml

@@ -12,7 +12,7 @@ development = ["bevy/dynamic_linking", "bevy/file_watcher"]
 debug_features = ["bevy/free_camera"]
 
 [dependencies]
-bevy = { version = "0.19", features = ["asset_processor", "basis-universal", "bevy_settings"] }
+bevy = { version = "0.19", features = ["asset_processor", "basis-universal", "compressed_image_saver", "bevy_settings"] }
 # Loads the scenes you author in the editor (assets/*.bsn) and builds
 # physics colliders from them. An ordinary dependency; remove it if you
 # stop using authored scenes.

scripts/install-blender.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+version="5.2.2"
+sha256="84098912789dc450e95697c4184fb8a90acbe5111c2ba4aede3fecb57806a168"
+install_dir="${1:-${BLENDER_INSTALL_DIR:-${HOME}/.local/blender-${version}}}"
+
+if [[ "$(uname -s)" != Linux || "$(uname -m)" != x86_64 ]]; then
+    echo "error: this installer currently supports Linux x86_64 only" >&2
+    exit 1
+fi
+
+if [[ -x "$install_dir/blender" ]]; then
+    "$install_dir/blender" --version | head -n 1
+    exit 0
+fi
+
+mkdir -p "$(dirname "$install_dir")"
+tmp_dir="$(mktemp -d)"
+trap 'rm -rf "$tmp_dir"' EXIT
+
+archive="blender-${version}-linux-x64.tar.xz"
+url="https://download.blender.org/release/Blender5.2/${archive}"
+
+curl --fail --location --silent --show-error --output "$tmp_dir/$archive" "$url"
+printf '%s  %s\n' "$sha256" "$tmp_dir/$archive" | sha256sum --check --status
+tar --extract --xz --file "$tmp_dir/$archive" --directory "$tmp_dir"
+mv "$tmp_dir/blender-${version}-linux-x64" "$install_dir"
+
+"$install_dir/blender" --version | head -n 1

src/blend_asset.rs

@@ -0,0 +1,394 @@
+//! Blender `.blend` source processing.
+//!
+//! Blender is used as an offline importer. The processed result is a normal
+//! GLB, so the runtime continues to use Bevy's built-in glTF loader.
+
+use bevy::{
+    asset::{
+        AssetLoader, AssetPath, AsyncWriteExt, LoadContext,
+        io::{Reader, Writer},
+        processor::LoadTransformAndSave,
+        saver::{AssetSaver, SavedAsset},
+        transformer::{AssetTransformer, TransformedAsset},
+    },
+    gltf::GltfLoader,
+    prelude::*,
+    reflect::TypePath,
+};
+use serde::Deserialize;
+use std::{
+    collections::HashMap,
+    fs, io,
+    path::{Path, PathBuf},
+    process::Command,
+    time::{SystemTime, UNIX_EPOCH},
+};
+
+use crate::fighter::animation::AnimKind;
+
+const EXPORT_SCRIPT: &str = include_str!("blend_asset/export.py");
+
+#[derive(Asset, TypePath)]
+struct BlendSource {
+    glb: Vec<u8>,
+}
+
+#[derive(Default, TypePath)]
+struct BlendSourceLoader;
+
+#[derive(Debug, Deserialize)]
+struct ExportManifest {
+    dependencies: Vec<String>,
+}
+
+#[derive(Debug, Deserialize)]
+struct AnimationManifest {
+    animations: HashMap<AnimKind, String>,
+}
+
+impl AssetLoader for BlendSourceLoader {
+    type Asset = BlendSource;
+    type Settings = ();
+    type Error = io::Error;
+
+    async fn load(
+        &self,
+        reader: &mut dyn Reader,
+        _: &Self::Settings,
+        load_context: &mut LoadContext<'_>,
+    ) -> Result<Self::Asset, Self::Error> {
+        let mut source_bytes = Vec::new();
+        reader.read_to_end(&mut source_bytes).await?;
+
+        let temp = TempDir::new()?;
+        let source_path = locate_source(load_context.path().path());
+        let blend_path = if let Some(path) = source_path.as_deref() {
+            path.to_path_buf()
+        } else {
+            let path = temp.path().join("source.blend");
+            fs::write(&path, source_bytes)?;
+            path
+        };
+        let output = temp.path().join("export.gltf");
+        let script = temp.path().join("export.py");
+        let actions = referenced_actions(load_context, &asset_root()).await?;
+        let actions_path = temp.path().join("actions.json");
+        fs::write(
+            &actions_path,
+            serde_json::to_vec(&actions).map_err(io::Error::other)?,
+        )?;
+        fs::write(&script, EXPORT_SCRIPT)?;
+
+        let result = Command::new(std::env::var_os("BLENDER").unwrap_or_else(|| "blender".into()))
+            .arg("--background")
+            .arg(&blend_path)
+            .arg("--python")
+            .arg(&script)
+            .arg("--")
+            .arg(&output)
+            .arg(&actions_path)
+            .arg(&blend_path)
+            .output()
+            .map_err(|error| io::Error::other(format!("failed to start Blender: {error}")))?;
+        if !result.status.success() {
+            return Err(io::Error::other(format!(
+                "Blender export failed with {}:\n{}\n{}",
+                result.status,
+                String::from_utf8_lossy(&result.stdout),
+                String::from_utf8_lossy(&result.stderr)
+            )));
+        }
+
+        let manifest: ExportManifest =
+            serde_json::from_slice(&fs::read(temp.path().join("export-manifest.json"))?)
+                .map_err(|error| io::Error::new(io::ErrorKind::InvalidData, error))?;
+
+        let asset_root = asset_root();
+        let mut dependencies = manifest.dependencies;
+        let document: serde_json::Value = serde_json::from_slice(&fs::read(&output)?)
+            .map_err(|error| io::Error::new(io::ErrorKind::InvalidData, error))?;
+        validate_export(&document, &output)?;
+        if let Some(images) = document.get("images").and_then(serde_json::Value::as_array) {
+            for image in images {
+                if let Some(uri) = image.get("uri").and_then(serde_json::Value::as_str) {
+                    let path = temp.path().join(uri);
+                    dependencies.push(path.to_string_lossy().into_owned());
+                }
+            }
+        }
+
+        let mut seen = std::collections::HashSet::new();
+        for dependency in dependencies {
+            let physical = PathBuf::from(&dependency);
+            let Some(asset_path) = physical_to_asset_path(&physical, &asset_root) else {
+                continue;
+            };
+            if seen.insert(asset_path.clone()) {
+                // This read is intentionally discarded: it registers the file and
+                // its processed hash as a processor dependency.
+                load_context
+                    .read_asset_bytes(asset_path)
+                    .await
+                    .map_err(|error| {
+                        io::Error::other(format!("failed to read blend dependency: {error}"))
+                    })?;
+            }
+        }
+
+        let glb = make_glb(&output, &temp, load_context.path().path(), &asset_root)?;
+        Ok(BlendSource { glb })
+    }
+
+    fn extensions(&self) -> &[&str] {
+        &["blend"]
+    }
+}
+
+fn validate_export(document: &serde_json::Value, output: &Path) -> io::Result<()> {
+    for key in ["scenes", "nodes", "meshes"] {
+        let count = document
+            .get(key)
+            .and_then(serde_json::Value::as_array)
+            .map_or(0, Vec::len);
+        if count == 0 {
+            return Err(io::Error::new(
+                io::ErrorKind::InvalidData,
+                format!("Blender export {} contains no {key}", output.display()),
+            ));
+        }
+    }
+    Ok(())
+}
+
+async fn referenced_actions(
+    load_context: &mut LoadContext<'_>,
+    root: &Path,
+) -> io::Result<Vec<String>> {
+    let model_path = load_context.path().path();
+    let Some(stem) = model_path.file_stem().and_then(|stem| stem.to_str()) else {
+        return Ok(Vec::new());
+    };
+    let manifest_path = model_path
+        .parent()
+        .unwrap_or_else(|| Path::new(""))
+        .join(format!("{stem}.fighter.ron"));
+    if !root.join(&manifest_path).is_file() {
+        return Ok(Vec::new());
+    }
+    let bytes = load_context
+        .read_asset_bytes(manifest_path)
+        .await
+        .map_err(|error| io::Error::other(error.to_string()))?;
+    let manifest: AnimationManifest = ron::de::from_bytes(&bytes)
+        .map_err(|error| io::Error::new(io::ErrorKind::InvalidData, error))?;
+    Ok(manifest.animations.into_values().collect())
+}
+
+#[derive(Asset, TypePath)]
+struct ProcessedBlend {
+    bytes: Vec<u8>,
+}
+
+#[derive(Default, TypePath)]
+struct BlendTransformer;
+
+impl AssetTransformer for BlendTransformer {
+    type AssetInput = BlendSource;
+    type AssetOutput = ProcessedBlend;
+    type Settings = ();
+    type Error = io::Error;
+
+    async fn transform<'a>(
+        &'a self,
+        source: TransformedAsset<Self::AssetInput>,
+        _: &'a Self::Settings,
+    ) -> Result<TransformedAsset<Self::AssetOutput>, Self::Error> {
+        let bytes = source.glb.clone();
+        Ok(source.replace_asset(ProcessedBlend { bytes }))
+    }
+}
+
+#[derive(Default, TypePath)]
+struct BlendSaver;
+
+impl AssetSaver for BlendSaver {
+    type Asset = ProcessedBlend;
+    type Settings = ();
+    type OutputLoader = GltfLoader;
+    type Error = io::Error;
+
+    async fn save(
+        &self,
+        writer: &mut Writer,
+        asset: SavedAsset<'_, '_, Self::Asset>,
+        _: &Self::Settings,
+        _: AssetPath<'_>,
+    ) -> Result<<Self::OutputLoader as AssetLoader>::Settings, Self::Error> {
+        writer.write_all(&asset.bytes).await?;
+        Ok(default())
+    }
+}
+
+type BlendProcessor = LoadTransformAndSave<BlendSourceLoader, BlendTransformer, BlendSaver>;
+
+pub struct BlendAssetProcessingPlugin;
+
+impl Plugin for BlendAssetProcessingPlugin {
+    fn build(&self, app: &mut App) {
+        app.init_asset::<BlendSource>()
+            .init_asset::<ProcessedBlend>()
+            .register_asset_loader(BlendSourceLoader)
+            .register_asset_processor(BlendProcessor::new(BlendTransformer, BlendSaver))
+            .set_default_asset_processor::<BlendProcessor>("blend");
+    }
+}
+
+struct TempDir(PathBuf);
+
+impl TempDir {
+    fn new() -> io::Result<Self> {
+        let stamp = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_nanos();
+        let path =
+            std::env::temp_dir().join(format!("shinespark-blend-{}-{stamp}", std::process::id()));
+        fs::create_dir_all(&path)?;
+        Ok(Self(path))
+    }
+    fn path(&self) -> &Path {
+        &self.0
+    }
+}
+
+impl Drop for TempDir {
+    fn drop(&mut self) {
+        let _ = fs::remove_dir_all(&self.0);
+    }
+}
+
+fn asset_root() -> PathBuf {
+    std::env::var_os("BEVY_ASSET_ROOT")
+        .map(PathBuf::from)
+        .unwrap_or_else(|| std::env::current_dir().unwrap_or_default().join("assets"))
+}
+
+fn locate_source(path: &Path) -> Option<PathBuf> {
+    let root = asset_root();
+    [root.join(path), PathBuf::from(path)]
+        .into_iter()
+        .find(|candidate| candidate.is_file())
+}
+
+fn physical_to_asset_path(path: &Path, root: &Path) -> Option<String> {
+    let canonical = fs::canonicalize(path).ok()?;
+    let root = fs::canonicalize(root).ok()?;
+    let relative = canonical.strip_prefix(root).ok()?;
+    Some(relative.to_string_lossy().replace('\\', "/"))
+}
+
+fn make_glb(
+    gltf_path: &Path,
+    temp: &TempDir,
+    model_asset_path: &Path,
+    asset_root: &Path,
+) -> io::Result<Vec<u8>> {
+    let mut json: serde_json::Value = serde_json::from_slice(&fs::read(gltf_path)?)
+        .map_err(|error| io::Error::new(io::ErrorKind::InvalidData, error))?;
+    let bin_name = json["buffers"][0]["uri"].as_str().ok_or_else(|| {
+        io::Error::new(io::ErrorKind::InvalidData, "glTF has no binary buffer URI")
+    })?;
+    let mut bin = fs::read(temp.path().join(bin_name))?;
+    let model_parent = model_asset_path.parent().unwrap_or_else(|| Path::new(""));
+    let image_count = json["images"].as_array().map_or(0, Vec::len);
+    if image_count > 0 && !json["bufferViews"].is_array() {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidData,
+            "glTF bufferViews are not an array",
+        ));
+    }
+    for index in 0..image_count {
+        let uri = json["images"][index]
+            .get("uri")
+            .and_then(serde_json::Value::as_str)
+            .map(str::to_owned);
+        let Some(uri) = uri else { continue };
+        if uri.starts_with("data:") {
+            continue;
+        }
+        let uri_path = temp.path().join(uri);
+        if let Some(asset_path) = physical_to_asset_path(&uri_path, asset_root) {
+            json["images"][index]["uri"] =
+                serde_json::Value::String(relative_uri(model_parent, Path::new(&asset_path)));
+        } else {
+            let bytes = fs::read(&uri_path)?;
+            while bin.len() % 4 != 0 {
+                bin.push(0);
+            }
+            let offset = bin.len();
+            bin.extend_from_slice(&bytes);
+            let mime = mime_type(&uri_path);
+            let view = json["bufferViews"].as_array().unwrap().len();
+            json["bufferViews"]
+                .as_array_mut()
+                .unwrap()
+                .push(serde_json::json!({
+                    "buffer": 0,
+                    "byteOffset": offset,
+                    "byteLength": bytes.len(),
+                }));
+            json["images"][index].as_object_mut().unwrap().remove("uri");
+            json["images"][index]["bufferView"] = serde_json::Value::from(view);
+            json["images"][index]["mimeType"] = serde_json::Value::String(mime.to_owned());
+        }
+    }
+    json["buffers"][0]["byteLength"] = serde_json::Value::from(bin.len());
+    json["buffers"][0].as_object_mut().unwrap().remove("uri");
+    let mut json_bytes = serde_json::to_vec(&json).map_err(io::Error::other)?;
+    while json_bytes.len() % 4 != 0 {
+        json_bytes.push(b' ');
+    }
+    while bin.len() % 4 != 0 {
+        bin.push(0);
+    }
+    let length = 12 + 8 + json_bytes.len() + 8 + bin.len();
+    let mut glb = Vec::with_capacity(length);
+    glb.extend_from_slice(b"glTF");
+    glb.extend_from_slice(&2u32.to_le_bytes());
+    glb.extend_from_slice(&(length as u32).to_le_bytes());
+    glb.extend_from_slice(&(json_bytes.len() as u32).to_le_bytes());
+    glb.extend_from_slice(b"JSON");
+    glb.extend_from_slice(&json_bytes);
+    glb.extend_from_slice(&(bin.len() as u32).to_le_bytes());
+    glb.extend_from_slice(b"BIN\0");
+    glb.extend_from_slice(&bin);
+    Ok(glb)
+}
+
+fn relative_uri(from: &Path, to: &Path) -> String {
+    let from: Vec<_> = from.components().collect();
+    let to: Vec<_> = to.components().collect();
+    let common = from.iter().zip(&to).take_while(|(a, b)| a == b).count();
+    let mut result = PathBuf::new();
+    for _ in common..from.len() {
+        result.push("..");
+    }
+    for component in &to[common..] {
+        result.push(component.as_os_str());
+    }
+    result.to_string_lossy().replace('\\', "/")
+}
+
+fn mime_type(path: &Path) -> &'static str {
+    match path
+        .extension()
+        .and_then(|e| e.to_str())
+        .unwrap_or_default()
+        .to_ascii_lowercase()
+        .as_str()
+    {
+        "jpg" | "jpeg" => "image/jpeg",
+        "webp" => "image/webp",
+        _ => "image/png",
+    }
+}

src/blend_asset/export.py

@@ -0,0 +1,80 @@
+import bpy
+import json
+import os
+import sys
+
+
+def main():
+    output = sys.argv[sys.argv.index("--") + 1]
+    actions_path = sys.argv[sys.argv.index("--") + 2]
+    source_path = sys.argv[sys.argv.index("--") + 3]
+    loaded_path = os.path.realpath(bpy.data.filepath)
+    expected_path = os.path.realpath(source_path)
+    if loaded_path != expected_path:
+        raise RuntimeError(
+            f"Blender loaded {loaded_path!r} instead of {expected_path!r}"
+        )
+    if not bpy.data.objects or not bpy.data.meshes:
+        raise RuntimeError("Blender loaded an empty scene")
+    with open(actions_path) as file:
+        actions_to_keep = set(json.load(file))
+
+    for obj in bpy.data.objects:
+        if not obj.animation_data:
+            continue
+        for track in list(obj.animation_data.nla_tracks):
+            if track.name.startswith("[Action Stash]"):
+                obj.animation_data.nla_tracks.remove(track)
+
+    nla_tracks = [
+        track
+        for obj in bpy.data.objects
+        if obj.animation_data
+        for track in obj.animation_data.nla_tracks
+    ]
+    use_nla_tracks = bool(nla_tracks)
+
+    # For blends without NLA tracks, use the actions referenced by the fighter
+    # manifest instead of sampling every source action.
+    if not use_nla_tracks and actions_to_keep:
+        from io_scene_gltf2 import GLTF2_filter_action
+
+        if not hasattr(bpy.types.Scene, "gltf_action_filter"):
+            bpy.types.Scene.gltf_action_filter = bpy.props.CollectionProperty(
+                type=GLTF2_filter_action
+            )
+        scene = bpy.context.scene
+        scene.gltf_action_filter.clear()
+        for action in bpy.data.actions:
+            item = scene.gltf_action_filter.add()
+            item.action = action
+            item.keep = action.name in actions_to_keep
+
+    bpy.ops.export_scene.gltf(
+        filepath=output,
+        export_format="GLTF_SEPARATE",
+        export_keep_originals=True,
+        export_extras=True,
+        export_animations=True,
+        export_skins=True,
+        export_morph=True,
+        export_yup=True,
+        export_def_bones=True,
+        export_action_filter=False,
+        export_animation_mode="NLA_TRACKS" if use_nla_tracks else "ACTIONS",
+    )
+
+    dependencies = []
+    for image in bpy.data.images:
+        if image.source not in {"FILE", "TILED"}:
+            continue
+        path = image.filepath_raw or image.filepath
+        if path and not image.packed_file:
+            dependencies.append(bpy.path.abspath(path))
+
+    with open(os.path.join(os.path.dirname(output), "export-manifest.json"), "w") as file:
+        json.dump({"dependencies": sorted(set(dependencies))}, file)
+
+
+if __name__ == "__main__":
+    main()

src/debug_tools/save_state.rs

@@ -1,12 +1,22 @@
 use bevy::prelude::*;
 
 use crate::{
-    camera::MatchCamera, fighter::{
-        FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop, FighterHitstopShake, FighterPreviousFacingDirection, FighterPreviousTranslation, FighterTranslation, FighterVelocity, Grounded, animation::FighterAnimationFrame, attack::{
+    camera::MatchCamera,
+    fighter::{
+        FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop, FighterHitstopShake,
+        FighterPreviousFacingDirection, FighterPreviousTranslation, FighterSurfaceState,
+        FighterTranslation, FighterVelocity,
+        animation::FighterAnimationFrame,
+        attack::{
             FighterDamage, FighterKnockbackVelocity, FighterPendingHitReaction, FighterPendingHits,
             FighterSolvedHurtboxes, FighterStaleMoveQueue,
-        }, baked_animation::FighterBoneMatrices, state::FighterState,
-    }, input::FighterInput, player::Player, stage::line::StageCollision,
+        },
+        baked_animation::FighterBoneMatrices,
+        state::FighterState,
+    },
+    input::FighterInput,
+    player::Player,
+    stage::line::StageCollision,
 };
 
 #[derive(Resource, Default)]
@@ -44,7 +54,7 @@ struct FighterCheckpoint {
     hitboxes: FighterHitboxes,
     solved_hurtboxes: FighterSolvedHurtboxes,
     bone_matrices: FighterBoneMatrices,
-    grounded: bool,
+    surface: FighterSurfaceState,
 }
 
 pub(super) fn save_or_restore(world: &mut World) {
@@ -143,11 +153,7 @@ pub(super) fn save_or_restore(world: &mut World) {
         entity.insert(saved.hitboxes.clone());
         entity.insert(saved.solved_hurtboxes.clone());
         entity.insert(saved.bone_matrices.clone());
-        if saved.grounded {
-            entity.insert(Grounded);
-        } else {
-            entity.remove::<Grounded>();
-        }
+        entity.insert(saved.surface);
     }
     world.insert_resource(checkpoint.pending_hits.clone());
     world.insert_resource(checkpoint.stage_collision);
@@ -181,7 +187,7 @@ fn capture_fighter(world: &World, entity: Entity) -> Option<FighterCheckpoint> {
         hitboxes: fighter.get::<FighterHitboxes>()?.clone(),
         solved_hurtboxes: fighter.get::<FighterSolvedHurtboxes>()?.clone(),
         bone_matrices: fighter.get::<FighterBoneMatrices>()?.clone(),
-        grounded: fighter.contains::<Grounded>(),
+        surface: *fighter.get::<FighterSurfaceState>()?,
     })
 }
 

src/fighter/baked_animation/asset_baking.rs

@@ -2,8 +2,8 @@ use super::{
     BAKED_ANIMATION_FPS,
     runtime::{BakedAnimationClip, BakedFighterAnimations},
 };
-use crate::math::fixed_transform::FixedMat4;
 use crate::fighter::{animation::AnimKind, manifest::FighterManifest};
+use crate::math::fixed_transform::FixedMat4;
 use bevy::{
     asset::{
         AssetLoader, AssetPath, AsyncWriteExt, LoadContext,
@@ -51,6 +51,9 @@ impl AssetLoader for FighterBakeSourceLoader {
             .map_err(|error| io::Error::other(error.to_string()))?;
         let manifest: FighterManifest = ron::de::from_bytes(&manifest_bytes)
             .map_err(|error| io::Error::new(io::ErrorKind::InvalidData, error))?;
+        // `read_asset_bytes` uses the processor's processed asset source. This
+        // deliberately allows `model_path` to point at a `.blend`: the blend
+        // processor has already converted it to a hybrid GLB by this point.
         let model_bytes = load_context
             .read_asset_bytes(&manifest.model_path)
             .await

src/fighter/baked_animation/mod.rs

@@ -21,6 +21,7 @@ mod tests {
     use asset_baking::{
         Channel, ChannelValues, bake_gltf_document, baked_frame_count, sample_vec3,
     };
+    use serde_json::json;
     use std::collections::HashMap;
 
     #[test]
@@ -29,11 +30,7 @@ mod tests {
             "../../../assets/fighters/test/test.fighter.ron"
         ))
         .unwrap();
-        let (document, buffers, _) = gltf::import(concat!(
-            env!("CARGO_MANIFEST_DIR"),
-            "/assets/fighters/test/test_fighter.gltf"
-        ))
-        .unwrap();
+        let (document, buffers) = test_gltf(&manifest.animations);
         let baked = bake_gltf_document(document, buffers, &manifest.animations).unwrap();
 
         assert_eq!(baked.frame_rate, BAKED_ANIMATION_FPS);
@@ -51,6 +48,104 @@ mod tests {
         assert_eq!(baked.parents.len(), baked.bone_names.len());
     }
 
+    /// Builds the smallest glTF document that still exercises the complete
+    /// animation-baking path. Keeping this fixture in memory avoids making
+    /// unit tests depend on the production Blender asset or Blender itself.
+    fn test_gltf(
+        animations: &HashMap<AnimKind, String>,
+    ) -> (gltf::Document, Vec<gltf::buffer::Data>) {
+        let mut names: Vec<_> = animations.values().cloned().collect();
+        names.sort();
+        names.dedup();
+
+        let mut data = Vec::new();
+        let mut buffer_views = Vec::new();
+        let mut accessors = Vec::new();
+        let mut gltf_animations = Vec::new();
+
+        for name in names {
+            let duration: f32 = match name.as_str() {
+                "Idle_Loop_Game" => 2.0,
+                "Walk_Loop_IK_Game" | "Run_Game" => 0.533333361,
+                "Dash_Game" => 0.333333343,
+                "Jump_Land_Game" => 0.133333340,
+                "JumpB_Game" => 56.0 / 60.0,
+                _ => 0.0,
+            };
+            let input_offset = data.len();
+            data.extend_from_slice(&0.0_f32.to_le_bytes());
+            data.extend_from_slice(&duration.to_le_bytes());
+            let output_offset = data.len();
+            data.extend_from_slice(
+                &[0.0_f32, 0.0, 0.0]
+                    .into_iter()
+                    .flat_map(f32::to_le_bytes)
+                    .collect::<Vec<_>>(),
+            );
+            data.extend_from_slice(
+                &[1.0_f32, 0.0, 0.0]
+                    .into_iter()
+                    .flat_map(f32::to_le_bytes)
+                    .collect::<Vec<_>>(),
+            );
+
+            let input_view = buffer_views.len();
+            buffer_views.push(json!({
+                "buffer": 0,
+                "byteOffset": input_offset,
+                "byteLength": 8
+            }));
+            let output_view = buffer_views.len();
+            buffer_views.push(json!({
+                "buffer": 0,
+                "byteOffset": output_offset,
+                "byteLength": 24
+            }));
+            let input_accessor = accessors.len();
+            accessors.push(json!({
+                "bufferView": input_view,
+                "componentType": 5126,
+                "count": 2,
+                "type": "SCALAR",
+                "min": [0.0],
+                "max": [duration]
+            }));
+            let output_accessor = accessors.len();
+            accessors.push(json!({
+                "bufferView": output_view,
+                "componentType": 5126,
+                "count": 2,
+                "type": "VEC3"
+            }));
+            gltf_animations.push(json!({
+                "name": name,
+                "samplers": [{
+                    "input": input_accessor,
+                    "output": output_accessor,
+                    "interpolation": "LINEAR"
+                }],
+                "channels": [{
+                    "sampler": 0,
+                    "target": { "node": 0, "path": "translation" }
+                }]
+            }));
+        }
+
+        let document = json!({
+            "asset": { "version": "2.0" },
+            "scene": 0,
+            "scenes": [{ "nodes": [0] }],
+            "nodes": [{ "name": "root", "children": [1] }, { "name": "hand" }],
+            "buffers": [{ "byteLength": data.len() }],
+            "bufferViews": buffer_views,
+            "accessors": accessors,
+            "animations": gltf_animations
+        });
+        let bytes = serde_json::to_vec(&document).unwrap();
+        let gltf = gltf::Gltf::from_slice(&bytes).unwrap();
+        (gltf.document, vec![gltf::buffer::Data(data)])
+    }
+
     #[test]
     fn pose_sampling_wraps_repeating_frames_and_clamps_finished_frames() {
         let first = FixedMat4::IDENTITY;

src/fighter/mod.rs

@@ -18,6 +18,7 @@ pub mod hurtbox;
 pub mod manifest;
 pub mod motion;
 pub mod state;
+pub mod surface;
 pub mod visual;
 
 // The fighter components are re-exported so the rest of the crate can say
@@ -28,18 +29,29 @@ pub use attributes::FighterAttributes;
 pub use ecb::FighterECB;
 pub use manifest::FighterId;
 pub use motion::{
-    FighterPreviousFacingDirection, FighterPreviousTranslation, FighterTranslation,
-    FighterVelocity, Grounded,
+    FighterPreviousFacingDirection, FighterPreviousTranslation, FighterTranslation, FighterVelocity,
 };
+pub use surface::FighterSurfaceState;
 
 use crate::{
-    AppState, fighter::{
+    AppState,
+    fighter::{
         attack::{
             AttackKind, FighterAttackPlugin, FighterAttackScriptAssets, FighterDamage,
             FighterKnockbackVelocity, FighterPendingHitReaction, FighterSolvedHurtboxes,
             FighterStaleMoveQueue,
-        }, baked_animation::{FighterBoneIndexMap, FighterBoneMatrices}, manifest::FighterManifest, state::{FighterState, air::AirborneStateCommon, fall::FallState}, visual::FighterAnimations,
-    }, input::FighterInput, math::{int::FGi32, vec::FGVec2}, player::Player, schedule::GameplaySet, scripting::FighterAttackScript, stage::line::StageCollision,
+        },
+        baked_animation::{FighterBoneIndexMap, FighterBoneMatrices},
+        manifest::FighterManifest,
+        state::{FighterState, air::AirborneStateCommon, fall::FallState},
+        visual::FighterAnimations,
+    },
+    input::FighterInput,
+    math::{int::FGi32, vec::FGVec2},
+    player::Player,
+    schedule::GameplaySet,
+    scripting::FighterAttackScript,
+    stage::line::StageCollision,
 };
 use state::state_interrupt_system;
 
@@ -58,14 +70,14 @@ pub enum FighterFacingDirection {
 pub enum FighterHitstopShakeKind {
     #[default]
     Horizontal,
-    Vertical
+    Vertical,
 }
 
 #[derive(Component, Copy, Clone, Hash, Debug, PartialEq, Reflect, Default)]
 pub enum FighterHitstopShakeRole {
     #[default]
     Attacker,
-    Receiver
+    Receiver,
 }
 
 #[derive(Component, Default, Copy, Clone, Hash)]
@@ -73,7 +85,7 @@ pub struct FighterHitstopShake {
     pub remaining_frames: u32,
     pub total_frames: u32,
     pub kind: FighterHitstopShakeKind,
-    pub role: FighterHitstopShakeRole
+    pub role: FighterHitstopShakeRole,
 }
 
 #[derive(Component, Default, Copy, Clone, Hash)]
@@ -133,7 +145,7 @@ pub struct FighterVisual;
     FighterPendingHitReaction,
     FighterHitstop,
     FighterKnockbackVelocity,
-    FighterTranslation,
+    FighterTranslation
 )]
 pub struct Fighter {
     pub manifest: Handle<FighterManifest>,
@@ -200,8 +212,8 @@ impl Plugin for FighterPlugin {
             .checksum_component_with_hash::<FighterPreviousFacingDirection>()
             .rollback_component_with_copy::<animation::FighterAnimationFrame>()
             .checksum_component_with_hash::<animation::FighterAnimationFrame>()
-            .rollback_component_with_copy::<Grounded>()
-            .checksum_component_with_hash::<Grounded>()
+            .rollback_component_with_copy::<FighterSurfaceState>()
+            .checksum_component_with_hash::<FighterSurfaceState>()
             .rollback_component_with_copy::<FighterFacingDirection>()
             .rollback_component_with_copy::<FighterDamage>()
             .checksum_component_with_hash::<FighterDamage>()
@@ -259,7 +271,7 @@ pub struct FighterActiveAttack {
     pub active_hitboxes: Vec<usize>,
     pub solved_hitboxes: Vec<attack::FighterSolvedHitbox>,
     pub hit_fighters: Vec<Entity>,
-    pub stalled: bool
+    pub stalled: bool,
 }
 
 #[derive(Component, Clone, Debug, Default, Hash)]
@@ -284,6 +296,7 @@ pub fn spawn_fighter(
             Fighter { manifest: manifest },
             FighterFacingDirection::Right,
             FighterPreviousFacingDirection(FighterFacingDirection::Right),
+            FighterSurfaceState::Airborne,
             Transform::from_scale(Vec3::splat(model_scale.to_num())),
             (
                 FighterECB {

src/fighter/motion.rs

@@ -5,7 +5,7 @@ use bevy::prelude::*;
 use bevy_ggrs::GgrsFrameTiming;
 
 use crate::debug_tools::PresentationMotionMode;
-use crate::fighter::{FighterHitstopShake};
+use crate::fighter::FighterHitstopShake;
 use crate::game_settings::GameSettings;
 use crate::{
     fighter::{FighterECB, FighterFacingDirection, baked_animation::FixedMat4},
@@ -15,9 +15,6 @@ use crate::{
 #[derive(Component, Clone, Copy, Hash)]
 pub struct FighterPreviousFacingDirection(pub FighterFacingDirection);
 
-#[derive(Component, Clone, Copy, Hash)]
-pub struct Grounded;
-
 #[derive(Component, Deref, DerefMut, Default, Debug, Clone, Copy, Hash)]
 pub struct FighterVelocity(pub FGVec2);
 
@@ -82,19 +79,29 @@ pub fn apply_fighter_translation_to_visuals(
             0.0,
         );
 
-        if hitstop_shake.remaining_frames > 0 && hitstop_shake.total_frames > 0 && !game_settings.fighter_common.visual_shake_table.is_empty() {
+        if hitstop_shake.remaining_frames > 0
+            && hitstop_shake.total_frames > 0
+            && !game_settings.fighter_common.visual_shake_table.is_empty()
+        {
             let total = hitstop_shake.total_frames as f32;
             let curr = hitstop_shake.remaining_frames as f32;
             let elapsed = 1.0 - curr / total;
 
-            
-            let access_index = (hitstop_shake.remaining_frames as usize) % game_settings.fighter_common.visual_shake_table.len();
+            let access_index = (hitstop_shake.remaining_frames as usize)
+                % game_settings.fighter_common.visual_shake_table.len();
             let shake_multiplier = match hitstop_shake.role {
-                super::FighterHitstopShakeRole::Attacker => game_settings.fighter_common.attacker_visual_shake_multiplier,
+                super::FighterHitstopShakeRole::Attacker => {
+                    game_settings
+                        .fighter_common
+                        .attacker_visual_shake_multiplier
+                }
                 super::FighterHitstopShakeRole::Receiver => 1.0,
             };
-            let shake_amount: f32 = 1.0 - EaseFunction::QuinticIn.sample(elapsed).unwrap_or_default();
-            let shake_amount = game_settings.fighter_common.visual_shake_table[access_index] * shake_amount * shake_multiplier;
+            let shake_amount: f32 =
+                1.0 - EaseFunction::QuinticIn.sample(elapsed).unwrap_or_default();
+            let shake_amount = game_settings.fighter_common.visual_shake_table[access_index]
+                * shake_amount
+                * shake_multiplier;
 
             let shake_offset = match hitstop_shake.kind {
                 super::FighterHitstopShakeKind::Horizontal => Vec3::new(shake_amount, 0.0, 0.0),

src/fighter/state/air.rs

@@ -1,4 +1,3 @@
-use crate::fighter::state::ground::GroundedStateCommon;
 use crate::fighter::state::land::{LandingState, LandingType};
 use crate::fighter::state::{CollisionContext, FighterState};
 use crate::fighter::*;
@@ -30,7 +29,7 @@ pub fn process_fast_fall(
 pub fn integrate_gravity(
     velocity: &mut FighterVelocity,
     attributes: &FighterAttributes,
-    fast_fall: bool
+    fast_fall: bool,
 ) {
     velocity.y -= attributes.gravity;
 
@@ -84,7 +83,9 @@ pub fn apply_air_motion(
     velocity: &FighterVelocity,
     translation: &mut FighterTranslation,
     prev_translation: &mut FighterPreviousTranslation,
+    surface: &mut FighterSurfaceState,
 ) {
+    surface.leave_ground();
     // Vertical velocity should be 0 on the ground
     prev_translation.0 = translation.0;
     translation.0 += velocity.0;
@@ -94,10 +95,24 @@ pub fn update_standard_motion(
     ctx: &mut crate::fighter::state::UpdateContext,
     airborne_common: &mut AirborneStateCommon,
 ) {
-    process_fast_fall(airborne_common, ctx.input, &mut ctx.velocity, ctx.fighter_attributes);
-    integrate_gravity(ctx.velocity, ctx.fighter_attributes, airborne_common.is_fast_falling);
+    process_fast_fall(
+        airborne_common,
+        ctx.input,
+        &mut ctx.velocity,
+        ctx.fighter_attributes,
+    );
+    integrate_gravity(
+        ctx.velocity,
+        ctx.fighter_attributes,
+        airborne_common.is_fast_falling,
+    );
     apply_air_drift(ctx.velocity, ctx.fighter_attributes, ctx.input);
-    apply_air_motion(ctx.velocity, ctx.translation, ctx.prev_translation);
+    apply_air_motion(
+        ctx.velocity,
+        ctx.translation,
+        ctx.prev_translation,
+        ctx.surface,
+    );
 }
 
 pub fn collision_interrupt(
@@ -106,13 +121,8 @@ pub fn collision_interrupt(
 ) -> Option<FighterState> {
     let res = ctx.air_collide_with_stage()?;
     ctx.translation.0 = res.hit_position - ctx.ecb.get_bottom_point();
-    let grounded_common = GroundedStateCommon {
-        current_line_id: res.line_id,
-    };
-    Some(FighterState::Land(LandingState::create(
-        grounded_common,
-        landing_type,
-    )))
+    ctx.surface.land(res.line_id);
+    Some(FighterState::Land(LandingState::create(landing_type)))
 }
 
 #[cfg(test)]

src/fighter/state/air_dodge.rs

@@ -1,9 +1,16 @@
 use crate::{
     fighter::{
-        animation::AnimKind, state::{
-            CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext, UpdateContext, air::{self, AirborneStateCommon}, fall::FallState, land::LandingType,
+        animation::AnimKind,
+        state::{
+            CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext,
+            UpdateContext,
+            air::{self, AirborneStateCommon},
+            fall::FallState,
+            land::LandingType,
         },
-    }, input, math::vec::FGVec2,
+    },
+    input,
+    math::vec::FGVec2,
 };
 
 #[derive(Debug, Clone, Hash)]
@@ -16,7 +23,9 @@ impl FighterStateImpl for AirDodgeState {
 
     fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
         if state_context.is_current_animation_finished() {
-            Some(FighterState::Fall(FallState::new(AirborneStateCommon::default())))
+            Some(FighterState::Fall(FallState::new(
+                AirborneStateCommon::default(),
+            )))
         } else {
             None
         }
@@ -29,6 +38,7 @@ impl FighterStateImpl for AirDodgeState {
             state_context.velocity,
             state_context.translation,
             state_context.prev_translation,
+            state_context.surface,
         );
     }
 
@@ -45,10 +55,8 @@ impl FighterStateImpl for AirDodgeState {
         state_context.velocity.0 =
             self.direction * state_context.fighter_attributes.air_dodge_velocity;
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         false
     }
 }

src/fighter/state/dash.rs

@@ -5,52 +5,43 @@ use super::{
 use crate::fighter::FighterFacingDirection;
 use crate::fighter::animation::AnimKind;
 use crate::fighter::state::FighterState;
-use crate::fighter::state::ground::GroundedStateCommon;
 use crate::input::FighterCommands::{SmashMoveLeft, SmashMoveRight};
 
 #[derive(Debug, Clone, Hash)]
 pub struct DashState {
     direction: FighterFacingDirection,
-    pub ground_common: GroundedStateCommon,
 }
 
 impl DashState {
-    pub fn new(direction: FighterFacingDirection, ground_common: GroundedStateCommon) -> Self {
-        Self {
-            direction,
-            ground_common,
-        }
+    pub fn new(direction: FighterFacingDirection) -> Self {
+        Self { direction }
     }
 }
 
 impl FighterStateImpl for DashState {
     const NAME: &'static str = "Dash";
     fn check_interrupt(&self, ctx: &mut InterruptContext) -> Option<FighterState> {
-        let ground = &self.ground_common;
         let attributes = ctx.fighter_attributes;
 
         // A reverse dash can interrupt before IASA
         if let Some(direction) =
             check_smash_input_with_dir(ctx).filter(|direction| *direction != self.direction)
         {
-            return Some(FighterState::Dash(DashState::new(
-                direction,
-                ground.clone(),
-            )));
+            return Some(FighterState::Dash(DashState::new(direction)));
         }
 
-        if let Some(state) = ground::grounded_movement_common_interrupts(ctx, ground) {
+        if let Some(state) = ground::grounded_movement_common_interrupts(ctx) {
             return Some(state);
         }
 
         if ctx.is_current_animation_finished() {
-            return run::check_input(ctx, ground)
-                .or_else(|| walk::check_input(ctx, ground))
-                .or_else(|| wait::check_input(ctx, ground));
+            return run::check_input(ctx)
+                .or_else(|| walk::check_input(ctx))
+                .or_else(|| wait::check_input(ctx));
         }
 
         if ctx.get_current_animation_frame() > attributes.dash_acceleration_duration {
-            return run::check_input(ctx, ground);
+            return run::check_input(ctx);
         }
 
         None
@@ -106,12 +97,10 @@ impl FighterStateImpl for DashState {
         &mut self,
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
-        ground::collision_interrupt(state_context, &mut self.ground_common, true)
+        ground::collision_interrupt(state_context, true)
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         true
     }
 }
@@ -126,10 +115,6 @@ fn check_smash_input_with_dir(state_context: &InterruptContext) -> Option<Fighte
     }
 }
 
-pub fn check_input(
-    state_context: &InterruptContext,
-    ground_common: &GroundedStateCommon,
-) -> Option<FighterState> {
-    check_smash_input_with_dir(state_context)
-        .map(|dir| FighterState::Dash(DashState::new(dir, ground_common.clone())))
+pub fn check_input(state_context: &InterruptContext) -> Option<FighterState> {
+    check_smash_input_with_dir(state_context).map(|dir| FighterState::Dash(DashState::new(dir)))
 }

src/fighter/state/ground.rs

@@ -3,7 +3,8 @@
 //! bit-for-bit deterministic for rollback.
 
 use crate::fighter::state::{
-    CollisionContext, FighterState, InterruptContext, air, dash, fall, ground_attack, turn, wait, walk,
+    CollisionContext, FighterState, InterruptContext, air, dash, fall, ground_attack, turn, wait,
+    walk,
 };
 use crate::fighter::{
     FighterAttributes, FighterPreviousTranslation, FighterTranslation, FighterVelocity,
@@ -13,13 +14,6 @@ use crate::math::int::{FGWide, FGi32};
 use crate::math::vec::FGVec2;
 use crate::stage::line::{StageLineID, StagePoly, StagePolyLineSegment, StagePolyLineSegmentType};
 
-use bevy::prelude::*;
-
-#[derive(Reflect, Hash, Clone, Debug)]
-pub struct GroundedStateCommon {
-    pub current_line_id: StageLineID,
-}
-
 pub fn apply_grounded_friction(friction: FGi32, ground_vel: FGi32) -> FGi32 {
     if friction.abs() > ground_vel.abs() {
         -ground_vel
@@ -181,22 +175,23 @@ pub fn update_friction_motion(ctx: &mut crate::fighter::state::UpdateContext) {
 
 pub fn collide_with_stage_grounded(
     state_context: &mut CollisionContext,
-    ground_common: &mut GroundedStateCommon,
     can_walk_off: bool,
 ) -> GroundedMotionResult {
     let translation = &mut state_context.translation;
     let ecb = state_context.ecb;
     let stage_collision = state_context.stage_collision;
 
-    let stage_poly = stage_collision
-        .stage_polys
-        .get(ground_common.current_line_id.polygon);
+    let Some(current_line_id) = state_context.surface.line_id() else {
+        return GroundedMotionResult::InAir;
+    };
+
+    let stage_poly = stage_collision.stage_polys.get(current_line_id.polygon);
 
     if let Some(stage_poly) = stage_poly {
         let ecb_bottom_pos = translation.0 + ecb.get_bottom_point();
         match resolve_grounded_position(
             stage_poly,
-            ground_common.current_line_id.segment,
+            current_line_id.segment,
             ecb_bottom_pos,
             can_walk_off,
         ) {
@@ -216,30 +211,37 @@ pub fn collide_with_stage_grounded(
                             .0
                             .project_onto_normalized(current_segment.normal)
                 };
-                ground_common.current_line_id.segment = segment_idx;
+                state_context.surface.land(StageLineID {
+                    polygon: current_line_id.polygon,
+                    segment: segment_idx,
+                });
                 GroundedMotionResult::InGround
             }
-            GroundedPositionResult::InAir => GroundedMotionResult::InAir,
+            GroundedPositionResult::InAir => {
+                state_context.surface.leave_ground();
+                GroundedMotionResult::InAir
+            }
         }
     } else {
+        state_context.surface.leave_ground();
         GroundedMotionResult::InAir
     }
 }
 
-pub fn collision_interrupt(
-    ctx: &mut CollisionContext,
-    common: &mut GroundedStateCommon,
-    can_walk_off: bool,
-) -> Option<FighterState> {
-    match collide_with_stage_grounded(ctx, common, can_walk_off) {
+pub fn collision_interrupt(ctx: &mut CollisionContext, can_walk_off: bool) -> Option<FighterState> {
+    match collide_with_stage_grounded(ctx, can_walk_off) {
         GroundedMotionResult::InGround => None,
-        GroundedMotionResult::InAir => Some(FighterState::Fall(fall::FallState::new(air::AirborneStateCommon::default()))),
+        GroundedMotionResult::InAir => Some(FighterState::Fall(fall::FallState::new(
+            air::AirborneStateCommon::default(),
+        ))),
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::fighter::ecb::FighterPreviousECB;
+    use crate::fighter::{FighterECB, FighterSurfaceState};
     use crate::stage::line::StagePolyType;
 
     fn two_segment_floor() -> StagePoly {
@@ -346,28 +348,110 @@ mod tests {
             GroundedPositionResult::InAir
         ));
     }
+
+    #[test]
+    fn grounded_collision_updates_surface_segment() {
+        let stage_collision = crate::stage::line::StageCollision {
+            stage_polys: vec![two_segment_floor()],
+        };
+        let mut surface = FighterSurfaceState::Grounded {
+            line_id: StageLineID {
+                polygon: 0,
+                segment: 0,
+            },
+        };
+        let mut translation = FighterTranslation(FGVec2::lit("11", "0"));
+        let previous_translation = FighterPreviousTranslation(translation.0);
+        let mut velocity = FighterVelocity::default();
+        let ecb = FighterECB {
+            vertical_half: FGi32::ONE,
+            horizontal_half: FGi32::ONE,
+        };
+        let previous_ecb = FighterPreviousECB::from(ecb);
+        let mut context = CollisionContext {
+            translation: &mut translation,
+            prev_translation: &previous_translation,
+            velocity: &mut velocity,
+            surface: &mut surface,
+            ecb: &ecb,
+            prev_ecb: &previous_ecb,
+            stage_collision: &stage_collision,
+        };
+
+        assert!(matches!(
+            collide_with_stage_grounded(&mut context, true),
+            GroundedMotionResult::InGround
+        ));
+        assert_eq!(
+            surface.line_id(),
+            Some(StageLineID {
+                polygon: 0,
+                segment: 1,
+            })
+        );
+    }
+
+    #[test]
+    fn walking_off_edge_clears_surface_contact() {
+        let stage_collision = crate::stage::line::StageCollision {
+            stage_polys: vec![StagePoly::build(
+                StagePolyType::Platform,
+                &[
+                    (FGVec2::lit("0", "0"), StagePolyLineSegmentType::Floor),
+                    (FGVec2::lit("10", "0"), StagePolyLineSegmentType::Floor),
+                ],
+            )],
+        };
+        let mut surface = FighterSurfaceState::Grounded {
+            line_id: StageLineID {
+                polygon: 0,
+                segment: 0,
+            },
+        };
+        let mut translation = FighterTranslation(FGVec2::lit("11", "0"));
+        let previous_translation = FighterPreviousTranslation(translation.0);
+        let mut velocity = FighterVelocity::default();
+        let ecb = FighterECB {
+            vertical_half: FGi32::ONE,
+            horizontal_half: FGi32::ONE,
+        };
+        let previous_ecb = FighterPreviousECB::from(ecb);
+        let mut context = CollisionContext {
+            translation: &mut translation,
+            prev_translation: &previous_translation,
+            velocity: &mut velocity,
+            surface: &mut surface,
+            ecb: &ecb,
+            prev_ecb: &previous_ecb,
+            stage_collision: &stage_collision,
+        };
+
+        assert!(matches!(
+            collide_with_stage_grounded(&mut context, true),
+            GroundedMotionResult::InAir
+        ));
+        assert_eq!(surface, FighterSurfaceState::Airborne);
+    }
 }
 
 pub fn grounded_movement_common_interrupts(
     state_context: &InterruptContext,
-    ground_common: &GroundedStateCommon,
 ) -> Option<FighterState> {
-    super::jump::check_input(state_context, ground_common)
+    super::jump::check_input(state_context)
 }
 
 pub fn grounded_movement_standstill_common_interrupts(
     state_context: &InterruptContext,
-    ground_common: &GroundedStateCommon,
 ) -> Option<FighterState> {
-    if let Some(state) = ground_attack::check_interrupt(state_context, &ground_common) {
+    if let Some(state) = ground_attack::check_interrupt(state_context) {
         Some(state)
-    } else if let Some(state) = dash::check_input(state_context, &ground_common) {
+    } else if let Some(state) = dash::check_input(state_context) {
         Some(state)
-    } else if let Some(state) = turn::check_input(state_context, &ground_common) {
+    } else if let Some(state) = turn::check_input(state_context) {
         Some(state)
-    } else if let Some(state) = walk::check_input(state_context, &ground_common) {
+    } else if let Some(state) = walk::check_input(state_context) {
         Some(state)
-    } else if let Some(state) = wait::check_input(state_context, &ground_common) {
+    } else if let Some(state) = wait::check_input(state_context) {
         Some(state)
     } else {
         None

src/fighter/state/ground_attack.rs

@@ -2,14 +2,13 @@ use crate::fighter::{
     attack::{AttackKind, update_active_hitbox_list},
     state::{
         CollisionContext, EnterContext, ExitContext, FighterState, FighterStateImpl,
-        InterruptContext, UpdateContext, ground::GroundedStateCommon, wait::WaitState,
+        InterruptContext, UpdateContext, wait::WaitState,
     },
 };
 
 #[derive(Clone, Debug, Hash)]
 pub struct GroundAttackState {
     pub attack_kind: AttackKind,
-    pub grounded_common: GroundedStateCommon,
 }
 
 impl FighterStateImpl for GroundAttackState {
@@ -17,9 +16,7 @@ impl FighterStateImpl for GroundAttackState {
 
     fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
         if state_context.is_current_animation_finished() {
-            Some(FighterState::Wait(WaitState {
-                grounded_common: self.grounded_common.clone(),
-            }))
+            Some(FighterState::Wait(WaitState))
         } else {
             None
         }
@@ -53,7 +50,7 @@ impl FighterStateImpl for GroundAttackState {
             active_hitboxes: Vec::new(),
             solved_hitboxes: Vec::new(),
             hit_fighters: Vec::new(),
-            stalled: false
+            stalled: false,
         });
     }
 
@@ -67,18 +64,13 @@ impl FighterStateImpl for GroundAttackState {
     ) -> Option<FighterState> {
         None
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         true
     }
 }
 
-pub fn check_interrupt(
-    state_context: &InterruptContext,
-    grounded_common: &GroundedStateCommon,
-) -> Option<FighterState> {
+pub fn check_interrupt(state_context: &InterruptContext) -> Option<FighterState> {
     if state_context
         .input
         .has_command(crate::input::FighterCommands::Attack)
@@ -89,7 +81,6 @@ pub fn check_interrupt(
             .to_attack_kind_grounded();
         Some(FighterState::GroundAttack(GroundAttackState {
             attack_kind,
-            grounded_common: grounded_common.clone(),
         }))
     } else {
         None

src/fighter/state/hitstun.rs

@@ -7,7 +7,7 @@ use crate::{
             InterruptContext, UpdateContext,
             air::{self, AirborneStateCommon},
             fall::FallState,
-            ground::{GroundedStateCommon, collision_interrupt},
+            ground::collision_interrupt,
             land::LandingType,
             wait::WaitState,
         },
@@ -17,7 +17,7 @@ use crate::{
 
 #[derive(Clone, Debug, Hash)]
 pub enum HitstopStateKind {
-    Grounded(GroundedStateCommon),
+    Grounded,
     Airborne,
 }
 
@@ -43,7 +43,7 @@ impl FighterStateImpl for HitstunState {
 
     fn name(&self) -> String {
         let hitstop_kind = match self.hitstop_kind {
-            HitstopStateKind::Grounded(_) => "Grounded",
+            HitstopStateKind::Grounded => "Grounded",
             HitstopStateKind::Airborne => "Airborne",
         };
 
@@ -58,14 +58,10 @@ impl FighterStateImpl for HitstunState {
     fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
         if state_context.get_current_animation_frame() > self.hit_reaction.hitstun_frames {
             match &self.hitstop_kind {
-                HitstopStateKind::Grounded(grounded_state_common) => {
-                    Some(FighterState::Wait(WaitState {
-                        grounded_common: grounded_state_common.clone(),
-                    }))
-                }
-                HitstopStateKind::Airborne => {
-                    Some(FighterState::Fall(FallState::new(AirborneStateCommon::default())))
-                }
+                HitstopStateKind::Grounded => Some(FighterState::Wait(WaitState)),
+                HitstopStateKind::Airborne => Some(FighterState::Fall(FallState::new(
+                    AirborneStateCommon::default(),
+                ))),
             }
         } else {
             None
@@ -85,8 +81,9 @@ impl FighterStateImpl for HitstunState {
         }
 
         match self.hitstop_kind {
-            HitstopStateKind::Grounded(_) => {}
+            HitstopStateKind::Grounded => {}
             HitstopStateKind::Airborne => {
+                ctx.surface.leave_ground();
                 air::integrate_gravity(ctx.velocity, ctx.fighter_attributes, false);
             }
         }
@@ -103,7 +100,7 @@ impl FighterStateImpl for HitstunState {
 
     fn on_enter(&mut self, state_context: &mut EnterContext) {
         let animation = match self.hitstop_kind {
-            HitstopStateKind::Grounded(_) => AnimKind::FlinchGround,
+            HitstopStateKind::Grounded => AnimKind::FlinchGround,
             HitstopStateKind::Airborne => AnimKind::FlinchAir,
         };
         state_context.play_animation(animation, false);
@@ -116,9 +113,7 @@ impl FighterStateImpl for HitstunState {
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
         match &mut self.hitstop_kind {
-            HitstopStateKind::Grounded(grounded_state_common) => {
-                collision_interrupt(state_context, grounded_state_common, true)
-            }
+            HitstopStateKind::Grounded => collision_interrupt(state_context, true),
             HitstopStateKind::Airborne => {
                 air::collision_interrupt(state_context, LandingType::Normal)
             }
@@ -127,7 +122,7 @@ impl FighterStateImpl for HitstunState {
 
     fn is_visually_grounded<'a>(&'a self) -> bool {
         match self.hitstop_kind {
-            HitstopStateKind::Grounded(_) => true,
+            HitstopStateKind::Grounded => true,
             HitstopStateKind::Airborne => false,
         }
     }

src/fighter/state/jump.rs

@@ -2,10 +2,17 @@ use bevy::prelude::*;
 
 use crate::{
     fighter::{
-        animation::AnimKind, state::{
-            CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext, UpdateContext, air::{self, AirborneStateCommon}, air_dodge::{self, AirDodgeState}, ground::{self, GroundedStateCommon},
+        animation::AnimKind,
+        state::{
+            CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext,
+            UpdateContext,
+            air::{self, AirborneStateCommon},
+            air_dodge::{self, AirDodgeState},
+            ground,
         },
-    }, input::FighterCommands, math::{int::FGi32, vec::FGVec2},
+    },
+    input::FighterCommands,
+    math::{int::FGi32, vec::FGVec2},
 };
 #[derive(Debug, Hash, Clone, Copy)]
 pub enum JumpType {
@@ -22,14 +29,12 @@ pub struct JumpState {
 
 #[derive(Debug, Clone, Hash)]
 pub struct JumpSquatState {
-    pub grounded_common: GroundedStateCommon,
     pub duration_counter: u32,
 }
 
 impl JumpSquatState {
-    pub fn create(grounded_common: GroundedStateCommon) -> Self {
+    pub fn create() -> Self {
         Self {
-            grounded_common,
             duration_counter: 0,
         }
     }
@@ -69,7 +74,10 @@ impl FighterStateImpl for JumpSquatState {
             } else {
                 JumpType::ShortHop
             };
-            Some(FighterState::Jump(JumpState { jump_type, airborne_state_common: AirborneStateCommon::default() }))
+            Some(FighterState::Jump(JumpState {
+                jump_type,
+                airborne_state_common: AirborneStateCommon::default(),
+            }))
         } else {
             None
         }
@@ -84,17 +92,15 @@ impl FighterStateImpl for JumpSquatState {
         &mut self,
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
-        ground::collision_interrupt(state_context, &mut self.grounded_common, false)
+        ground::collision_interrupt(state_context, false)
     }
 
     fn on_enter(&mut self, state_context: &mut EnterContext) {
         state_context.play_animation(AnimKind::JumpSquat, false);
         state_context.input.clear_command(FighterCommands::Jump);
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         true
     }
 }
@@ -105,7 +111,7 @@ impl FighterStateImpl for JumpState {
         if state_context.input.has_command(FighterCommands::Jump) {
             Some(FighterState::Jump(JumpState {
                 jump_type: JumpType::DoubleJump,
-                airborne_state_common: AirborneStateCommon::default()
+                airborne_state_common: AirborneStateCommon::default(),
             }))
         } else {
             air_dodge::check_input(state_context)
@@ -176,22 +182,17 @@ impl FighterStateImpl for JumpState {
             crate::fighter::state::land::LandingType::Normal,
         )
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         false
     }
 }
 
-pub fn check_input(
-    state_context: &InterruptContext,
-    ground_common: &GroundedStateCommon,
-) -> Option<FighterState> {
+pub fn check_input(state_context: &InterruptContext) -> Option<FighterState> {
     state_context
         .input
         .has_command(FighterCommands::Jump)
-        .then(|| FighterState::JumpSquat(JumpSquatState::create(ground_common.clone())))
+        .then(|| FighterState::JumpSquat(JumpSquatState::create()))
 }
 
 pub fn check_input_double_jump(state_context: &InterruptContext) -> Option<FighterState> {
@@ -201,7 +202,7 @@ pub fn check_input_double_jump(state_context: &InterruptContext) -> Option<Fight
         .then(|| {
             FighterState::Jump(JumpState {
                 jump_type: JumpType::DoubleJump,
-                airborne_state_common: AirborneStateCommon::default()
+                airborne_state_common: AirborneStateCommon::default(),
             })
         })
 }

src/fighter/state/land.rs

@@ -3,7 +3,7 @@ use crate::fighter::{
     state::{
         CollisionContext, EnterContext, FighterState, FighterStateImpl, InterruptContext,
         UpdateContext, dash,
-        ground::{self, GroundedStateCommon, grounded_movement_standstill_common_interrupts},
+        ground::{self, grounded_movement_standstill_common_interrupts},
         walk,
     },
 };
@@ -16,16 +16,12 @@ pub enum LandingType {
 
 #[derive(Debug, Clone, Hash)]
 pub struct LandingState {
-    pub grounded_common: GroundedStateCommon,
     pub landing_type: LandingType,
 }
 
 impl LandingState {
-    pub fn create(grounded_common: GroundedStateCommon, landing_type: LandingType) -> Self {
-        Self {
-            grounded_common,
-            landing_type,
-        }
+    pub fn create(landing_type: LandingType) -> Self {
+        Self { landing_type }
     }
 }
 
@@ -34,14 +30,14 @@ impl FighterStateImpl for LandingState {
 
     fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
         if state_context.is_current_animation_finished() {
-            grounded_movement_standstill_common_interrupts(state_context, &self.grounded_common)
+            grounded_movement_standstill_common_interrupts(state_context)
         } else if state_context.get_current_animation_frame()
             >= state_context.fighter_attributes.landing_iasa
             && let LandingType::Normal = self.landing_type
         {
-            dash::check_input(state_context, &self.grounded_common).or_else(|| {
-                ground::grounded_movement_common_interrupts(state_context, &self.grounded_common)
-                    .or_else(|| walk::check_input(state_context, &self.grounded_common))
+            dash::check_input(state_context).or_else(|| {
+                ground::grounded_movement_common_interrupts(state_context)
+                    .or_else(|| walk::check_input(state_context))
             })
         } else {
             None
@@ -56,7 +52,7 @@ impl FighterStateImpl for LandingState {
         &mut self,
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
-        ground::collision_interrupt(state_context, &mut self.grounded_common, true)
+        ground::collision_interrupt(state_context, true)
     }
 
     fn on_enter(&mut self, state_context: &mut EnterContext) {
@@ -69,10 +65,8 @@ impl FighterStateImpl for LandingState {
             }
         };
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         true
     }
 }

src/fighter/state/mod.rs

@@ -7,7 +7,8 @@ use bevy::prelude::*;
 
 use crate::fighter::animation::{AnimKind, FighterAnimationFrame};
 use crate::fighter::attack::{
-    FighterAttackScriptAssets, FighterKnockbackVelocity, FighterPendingHitReaction, FighterStaleMoveQueue, HitStop,
+    FighterAttackScriptAssets, FighterKnockbackVelocity, FighterPendingHitReaction,
+    FighterStaleMoveQueue, HitStop,
 };
 use crate::fighter::attributes::FighterAttributes;
 use crate::fighter::baked_animation::BakedFighterAnimations;
@@ -16,7 +17,9 @@ use crate::fighter::manifest::FighterManifest;
 use crate::fighter::state::hitstun::HitstunState;
 use crate::fighter::visual::FighterAnimations;
 use crate::fighter::{
-    Fighter, FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop, FighterHitstopShake, FighterHitstopShakeKind, FighterHitstopShakeRole, FighterPreviousTranslation, FighterTranslation, FighterVelocity,
+    Fighter, FighterECB, FighterFacingDirection, FighterHitboxes, FighterHitstop,
+    FighterHitstopShake, FighterHitstopShakeKind, FighterHitstopShakeRole,
+    FighterPreviousTranslation, FighterSurfaceState, FighterTranslation, FighterVelocity,
 };
 use crate::game_settings::GameSettings;
 use crate::input::FighterInput;
@@ -95,9 +98,7 @@ pub trait FighterStateImpl: Sized {
         None
     }
 
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool;
+    fn is_visually_grounded<'a>(&'a self) -> bool;
 }
 
 pub struct AnimationStatus {
@@ -151,6 +152,7 @@ pub struct UpdateContext<'a> {
     pub input: &'a mut FighterInput,
     pub hitboxes: &'a mut FighterHitboxes,
     pub velocity: &'a mut FighterVelocity,
+    pub surface: &'a mut FighterSurfaceState,
     pub knockback_velocity: &'a mut FighterKnockbackVelocity,
     pub game_settings: &'a GameSettings,
     pub animation_frame: u32,
@@ -170,6 +172,7 @@ pub struct CollisionContext<'a> {
     pub translation: &'a mut FighterTranslation,
     pub prev_translation: &'a FighterPreviousTranslation,
     pub velocity: &'a mut FighterVelocity,
+    pub surface: &'a mut FighterSurfaceState,
     pub ecb: &'a FighterECB,
     pub prev_ecb: &'a FighterPreviousECB,
     pub stage_collision: &'a StageCollision,
@@ -212,6 +215,7 @@ pub struct FighterFrameQuery {
     pub input: &'static mut FighterInput,
     pub hitboxes: &'static mut FighterHitboxes,
     pub velocity: &'static mut FighterVelocity,
+    pub surface: &'static mut FighterSurfaceState,
     pub knockback_velocity: &'static mut FighterKnockbackVelocity,
     pub stale_move_queue: &'static mut FighterStaleMoveQueue,
     pub ecb: &'static FighterECB,
@@ -292,13 +296,14 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
             input: &mut self.input,
             hitboxes: &mut self.hitboxes,
             velocity: &mut self.velocity,
+            surface: &mut self.surface,
             knockback_velocity: &mut self.knockback_velocity,
             game_settings,
             animation_frame: self.animation_frame.frame,
             fighter_attributes: attributes,
             attack_scripts,
             attack_script_assets,
-            facing_direction: &self.facing_direction
+            facing_direction: &self.facing_direction,
         }
     }
 
@@ -310,6 +315,7 @@ impl<'w, 's> FighterFrameQueryItem<'w, 's> {
             translation: &mut self.translation,
             prev_translation: &self.prev_translation,
             velocity: &mut self.velocity,
+            surface: &mut self.surface,
             ecb: &self.ecb,
             prev_ecb: &self.prev_ecb,
             stage_collision,
@@ -400,7 +406,9 @@ pub fn state_interrupt_system(
 
         let new_state = if let Some(reaction) = pending_hit_reaction.take() {
             hitstop.remaining_frames = *reaction.hitstop_frames;
-            let shake_frames = reaction.hitstop_frames.calculate_shake_frames(&game_settings);
+            let shake_frames = reaction
+                .hitstop_frames
+                .calculate_shake_frames(&game_settings);
             hitstop_shake.role = FighterHitstopShakeRole::Receiver;
             hitstop_shake.total_frames = shake_frames;
             hitstop_shake.remaining_frames = shake_frames;
@@ -409,36 +417,26 @@ pub fn state_interrupt_system(
             } else {
                 FighterHitstopShakeKind::Vertical
             };
-            
-            let mut hitstop_kind = match &*state {
-                FighterState::Wait(value) => {
-                    hitstun::HitstopStateKind::Grounded(value.grounded_common.clone())
-                }
-                FighterState::Walk(value) => {
-                    hitstun::HitstopStateKind::Grounded(value.grounded_common.clone())
-                }
-                FighterState::Dash(value) => {
-                    hitstun::HitstopStateKind::Grounded(value.ground_common.clone())
-                }
-                FighterState::Run(value) => {
-                    hitstun::HitstopStateKind::Grounded(value.grounded_common.clone())
-                }
-                FighterState::Turn(value) => {
-                    hitstun::HitstopStateKind::Grounded(value.grounded_common.clone())
-                }
-                FighterState::GroundAttack(value) => {
-                    hitstun::HitstopStateKind::Grounded(value.grounded_common.clone())
-                }
-                _ => hitstun::HitstopStateKind::Airborne,
+
+            let mut hitstop_kind = if frame.surface.is_grounded() {
+                hitstun::HitstopStateKind::Grounded
+            } else {
+                hitstun::HitstopStateKind::Airborne
             };
 
-            if let hitstun::HitstopStateKind::Grounded(_) = hitstop_kind {
+            if let hitstun::HitstopStateKind::Grounded = hitstop_kind {
                 let straight_up_angle = FGi32::lit("90.0");
-                if reaction.hitstop_frames >= HitStop::new(game_settings.fighter_common.tumble_bounce_hitstop_threshold) {
+                if reaction.hitstop_frames
+                    >= HitStop::new(game_settings.fighter_common.tumble_bounce_hitstop_threshold)
+                {
                     hitstop_kind = hitstun::HitstopStateKind::Airborne;
                 // TODO: Use floor normal here
-                } else if reaction.launch_angle.abs_diff(straight_up_angle) < game_settings.fighter_common.attack_ground_to_airborne_transition_vertical_angle_threshold {
-                        hitstop_kind = hitstun::HitstopStateKind::Airborne;
+                } else if reaction.launch_angle.abs_diff(straight_up_angle)
+                    < game_settings
+                        .fighter_common
+                        .attack_ground_to_airborne_transition_vertical_angle_threshold
+                {
+                    hitstop_kind = hitstun::HitstopStateKind::Airborne;
                 } else {
                     // straight down is 270
                     let straight_down_angle = FGi32::lit("270.0");
@@ -450,6 +448,10 @@ pub fn state_interrupt_system(
                 }
             }
 
+            if matches!(hitstop_kind, hitstun::HitstopStateKind::Airborne) {
+                frame.surface.leave_ground();
+            }
+
             info!("Entering hitstop kind: {:?}", hitstop_kind);
             Some(FighterState::Hitstun(HitstunState::new(
                 reaction,

src/fighter/state/run.rs

@@ -6,19 +6,14 @@ use super::{
 };
 use crate::fighter::animation::AnimKind;
 use crate::fighter::state::FighterState;
-use crate::fighter::state::ground::GroundedStateCommon;
 
 #[derive(Component, Debug, Clone, Hash)]
-pub struct RunState {
-    pub grounded_common: GroundedStateCommon,
-}
+pub struct RunState;
 
 impl FighterStateImpl for RunState {
     const NAME: &'static str = "Run";
     fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
-        if let Some(state) =
-            ground::grounded_movement_common_interrupts(state_context, &self.grounded_common)
-        {
+        if let Some(state) = ground::grounded_movement_common_interrupts(state_context) {
             return Some(state);
         }
 
@@ -28,8 +23,7 @@ impl FighterStateImpl for RunState {
         {
             None
         } else {
-            walk::check_input(state_context, &self.grounded_common)
-                .or_else(|| wait::check_input(state_context, &self.grounded_common))
+            walk::check_input(state_context).or_else(|| wait::check_input(state_context))
         }
     }
 
@@ -62,26 +56,19 @@ impl FighterStateImpl for RunState {
         &mut self,
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
-        ground::collision_interrupt(state_context, &mut self.grounded_common, true)
+        ground::collision_interrupt(state_context, true)
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         true
     }
 }
 
-pub fn check_input(
-    state_context: &InterruptContext,
-    ground_state_common: &GroundedStateCommon,
-) -> Option<FighterState> {
+pub fn check_input(state_context: &InterruptContext) -> Option<FighterState> {
     let input_frame = state_context.input.get_last_frame();
     if input_frame.movement.x.abs() >= state_context.game_settings.input_common.run_stick_threshold
     {
-        return Some(FighterState::Run(RunState {
-            grounded_common: ground_state_common.clone(),
-        }));
+        return Some(FighterState::Run(RunState));
     }
     None
 }

src/fighter/state/turn.rs

@@ -1,13 +1,11 @@
 use super::{CollisionContext, EnterContext, FighterStateImpl, InterruptContext, UpdateContext};
 use crate::fighter::animation::AnimKind;
-use crate::fighter::state::ground::{self, GroundedStateCommon};
+use crate::fighter::state::ground;
 use crate::fighter::state::{FighterState, dash, jump, wait, walk};
 use crate::input::FighterCommands;
 
 #[derive(Debug, Clone, Hash)]
-pub struct TurnState {
-    pub grounded_common: GroundedStateCommon,
-}
+pub struct TurnState;
 
 impl FighterStateImpl for TurnState {
     const NAME: &'static str = "Turn";
@@ -19,19 +17,19 @@ impl FighterStateImpl for TurnState {
                 .input_common
                 .turn_into_dashback_window as u32
         {
-            if let Some(state) = dash::check_input(state_context, &self.grounded_common) {
+            if let Some(state) = dash::check_input(state_context) {
                 return Some(state);
             }
         }
-        if let Some(state) = jump::check_input(state_context, &self.grounded_common) {
+        if let Some(state) = jump::check_input(state_context) {
             *state_context.facing_direction = state_context.facing_direction.reverse();
             Some(state)
         } else if state_context.is_current_animation_finished() {
-            if let Some(state) = dash::check_input(state_context, &self.grounded_common) {
+            if let Some(state) = dash::check_input(state_context) {
                 Some(state)
-            } else if let Some(state) = walk::check_input(state_context, &self.grounded_common) {
+            } else if let Some(state) = walk::check_input(state_context) {
                 Some(state)
-            } else if let Some(state) = wait::check_input(state_context, &self.grounded_common) {
+            } else if let Some(state) = wait::check_input(state_context) {
                 Some(state)
             } else {
                 None
@@ -54,20 +52,15 @@ impl FighterStateImpl for TurnState {
         &mut self,
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
-        ground::collision_interrupt(state_context, &mut self.grounded_common, false)
+        ground::collision_interrupt(state_context, false)
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         true
     }
 }
 
-pub fn check_input(
-    state_context: &InterruptContext,
-    grounded_common: &GroundedStateCommon,
-) -> Option<FighterState> {
+pub fn check_input(state_context: &InterruptContext) -> Option<FighterState> {
     let input_frame = state_context.input.get_last_frame();
 
     let has_smash_input = state_context
@@ -81,9 +74,7 @@ pub fn check_input(
         && input_frame.movement.x.signum() != state_context.facing_direction.to_sign()
         && !has_smash_input
     {
-        return Some(FighterState::Turn(TurnState {
-            grounded_common: grounded_common.clone(),
-        }));
+        return Some(FighterState::Turn(TurnState));
     }
     None
 }

src/fighter/state/wait.rs

@@ -3,24 +3,18 @@ use super::{
 };
 use crate::fighter::animation::AnimKind;
 use crate::fighter::state::FighterState;
-use crate::fighter::state::ground::GroundedStateCommon;
 
 #[derive(Debug, Clone, Hash)]
-pub struct WaitState {
-    pub grounded_common: GroundedStateCommon,
-}
+pub struct WaitState;
 
 impl FighterStateImpl for WaitState {
     const NAME: &'static str = "Wait";
     fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
-        if let Some(state) =
-            ground::grounded_movement_common_interrupts(state_context, &self.grounded_common)
-        {
+        if let Some(state) = ground::grounded_movement_common_interrupts(state_context) {
             Some(state)
-        } else if let Some(state) = ground::grounded_movement_standstill_common_interrupts(
-            state_context,
-            &self.grounded_common,
-        ) {
+        } else if let Some(state) =
+            ground::grounded_movement_standstill_common_interrupts(state_context)
+        {
             // Don't transition into yourself
             if let FighterState::Wait(_) = state {
                 None
@@ -44,26 +38,19 @@ impl FighterStateImpl for WaitState {
         &mut self,
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
-        ground::collision_interrupt(state_context, &mut self.grounded_common, false)
+        ground::collision_interrupt(state_context, false)
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         true
     }
 }
 
-pub fn check_input(
-    state_context: &InterruptContext,
-    ground_state_common: &GroundedStateCommon,
-) -> Option<FighterState> {
+pub fn check_input(state_context: &InterruptContext) -> Option<FighterState> {
     let input_frame = state_context.input.get_last_frame();
 
     if input_frame.movement.x.abs() < state_context.game_settings.input_common.stick_deadzone {
-        return Some(FighterState::Wait(WaitState {
-            grounded_common: ground_state_common.clone(),
-        }));
+        return Some(FighterState::Wait(WaitState));
     }
     None
 }

src/fighter/state/walk.rs

@@ -4,23 +4,17 @@ use super::{
 };
 use crate::fighter::animation::AnimKind;
 use crate::fighter::state::FighterState;
-use crate::fighter::state::ground::GroundedStateCommon;
 
 #[derive(Debug, Clone, Hash)]
-pub struct WalkState {
-    pub grounded_common: GroundedStateCommon,
-}
+pub struct WalkState;
 
 impl FighterStateImpl for WalkState {
     const NAME: &'static str = "Walk";
     fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
-        if let Some(state) =
-            ground::grounded_movement_common_interrupts(state_context, &self.grounded_common)
-        {
+        if let Some(state) = ground::grounded_movement_common_interrupts(state_context) {
             return Some(state);
         }
-        wait::check_input(state_context, &self.grounded_common)
-            .or_else(|| dash::check_input(state_context, &self.grounded_common))
+        wait::check_input(state_context).or_else(|| dash::check_input(state_context))
     }
 
     fn on_enter(&mut self, state_context: &mut EnterContext) {
@@ -54,26 +48,19 @@ impl FighterStateImpl for WalkState {
         &mut self,
         state_context: &mut CollisionContext,
     ) -> Option<FighterState> {
-        ground::collision_interrupt(state_context, &mut self.grounded_common, false)
+        ground::collision_interrupt(state_context, false)
     }
-    
-    fn is_visually_grounded<'a>(
-        &'a self,
-    ) -> bool {
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
         true
     }
 }
 
-pub fn check_input(
-    state_context: &InterruptContext,
-    ground_state_common: &GroundedStateCommon,
-) -> Option<FighterState> {
+pub fn check_input(state_context: &InterruptContext) -> Option<FighterState> {
     let input_frame = state_context.input.get_last_frame();
 
     if !input_frame.movement.x.is_zero() {
-        return Some(FighterState::Walk(WalkState {
-            grounded_common: ground_state_common.clone(),
-        }));
+        return Some(FighterState::Walk(WalkState));
     }
 
     None

src/fighter/surface.rs

@@ -0,0 +1,62 @@
+use bevy::prelude::*;
+
+use crate::stage::line::StageLineID;
+
+/// The stage surface currently supporting a fighter.
+///
+/// This is physics state rather than fighter-state-machine state. Keeping it
+/// separate means grounded, landing, and hitstun states all share one source
+/// of truth for stage contact.
+#[derive(Component, Clone, Copy, Debug, Default, Hash, PartialEq, Eq)]
+pub enum FighterSurfaceState {
+    #[default]
+    Airborne,
+    Grounded {
+        line_id: StageLineID,
+    },
+}
+
+impl FighterSurfaceState {
+    pub fn is_grounded(self) -> bool {
+        matches!(self, Self::Grounded { .. })
+    }
+
+    pub fn line_id(self) -> Option<StageLineID> {
+        match self {
+            Self::Airborne => None,
+            Self::Grounded { line_id } => Some(line_id),
+        }
+    }
+
+    pub(crate) fn land(&mut self, line_id: StageLineID) {
+        *self = Self::Grounded { line_id };
+    }
+
+    pub(crate) fn leave_ground(&mut self) {
+        *self = Self::Airborne;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn contact_lifecycle_has_one_source_of_truth() {
+        let mut surface = FighterSurfaceState::default();
+        assert!(!surface.is_grounded());
+        assert_eq!(surface.line_id(), None);
+
+        let line_id = StageLineID {
+            polygon: 2,
+            segment: 3,
+        };
+        surface.land(line_id);
+        assert!(surface.is_grounded());
+        assert_eq!(surface.line_id(), Some(line_id));
+
+        surface.leave_ground();
+        assert!(!surface.is_grounded());
+        assert_eq!(surface.line_id(), None);
+    }
+}

src/lib.rs

@@ -38,6 +38,7 @@ use crate::{
 };
 
 mod args;
+pub mod blend_asset;
 pub mod camera;
 pub mod debug_tools;
 pub mod fighter;
@@ -89,6 +90,7 @@ pub struct GameAssetPlugin;
 impl Plugin for GameAssetPlugin {
     fn build(&self, app: &mut App) {
         app.add_plugins((
+            blend_asset::BlendAssetProcessingPlugin,
             RonAssetPlugin::<FighterManifest>::create("fighter.ron"),
             RonAssetPlugin::<StageManifest>::create("stage.ron"),
             RonAssetPlugin::<GameSettings>::create("ron"),

src/main.rs

@@ -1,6 +1,7 @@
 use bevy::asset::AssetMode::Processed;
 #[cfg(feature = "debug_features")]
 use bevy::camera_controller::free_camera::FreeCameraPlugin;
+use bevy::gltf::GltfPlugin;
 use bevy::image::{ImageAddressMode, ImagePlugin, ImageSamplerDescriptor};
 use bevy::prelude::*;
 #[cfg(feature = "debug_features")]
@@ -12,14 +13,18 @@ fn main() -> AppExit {
     // A `Repeat` sampler so the tileable materials authored in the
     // editor render the same way at runtime; Bevy's default
     // `ClampToEdge` smears texture edges on brush geometry.
+    let default_sampler = ImageSamplerDescriptor::linear()
+        .set_address_mode(ImageAddressMode::Repeat)
+        .set_anisotropic_filter(16)
+        .clone();
+
     let default_plugins = DefaultPlugins
         .set(ImagePlugin {
-            default_sampler: ImageSamplerDescriptor {
-                address_mode_u: ImageAddressMode::Repeat,
-                address_mode_v: ImageAddressMode::Repeat,
-                address_mode_w: ImageAddressMode::Repeat,
-                ..ImageSamplerDescriptor::linear()
-            },
+            default_sampler: default_sampler.clone(),
+        })
+        .set(GltfPlugin {
+            default_sampler,
+            ..default()
         })
         .set(AssetPlugin {
             mode: Processed,

src/stage/line.rs

@@ -26,7 +26,7 @@ pub enum StagePolyType {
     Platform,
 }
 
-#[derive(Reflect, Hash, Debug, Clone, Copy, Default)]
+#[derive(Reflect, Hash, Debug, Clone, Copy, Default, PartialEq, Eq)]
 pub struct StageLineID {
     pub polygon: usize,
     pub segment: usize,