Implement animation root motion deltas (#84)

Implements root motion and adds a dash attack.

Reviewed-on: #84
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

src/fighter/baked_animation/runtime.rs

@@ -14,6 +14,7 @@ use crate::{
     },
     math::fixed_transform::FixedMat4,
     math::int::FGi32,
+    math::vec3::FGVec3,
 };
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
@@ -55,6 +56,31 @@ impl BakedFighterAnimations {
     pub fn frame_count(&self, kind: AnimKind) -> Option<u32> {
         self.clip(kind).map(|clip| clip.frames.len() as u32)
     }
+    pub fn root_motion_cycle_delta(
+        &self,
+        kind: AnimKind,
+        bone: &str,
+        model_scale: FGi32,
+    ) -> Option<FGVec3> {
+        let last = self.frame_count(kind)?.saturating_sub(1);
+        let first = FighterAnimationFrame {
+            kind,
+            frame: 0,
+            repeat: false,
+        };
+        let last = FighterAnimationFrame {
+            kind,
+            frame: last,
+            repeat: false,
+        };
+        Some(
+            self.sample_bone_model_transform(&last, bone, model_scale)?
+                .get_translation()
+                - self
+                    .sample_bone_model_transform(&first, bone, model_scale)?
+                    .get_translation(),
+        )
+    }
     /// Samples one bone in model space without depending on the runtime's
     /// previous-frame buffers. Tooling uses this when the user scrubs between
     /// unrelated frames.
@@ -95,6 +121,12 @@ pub struct FighterBoneMatrices {
     previous_local_matrices: Vec<FixedMat4>,
     model_matrices: Vec<Option<FixedMat4>>,
     presentation_kind: Option<AnimKind>,
+    previous_animation_frame: Option<FighterAnimationFrame>,
+    /// The raw, scaled model-space root translation used as the baseline for
+    /// root-motion extraction.  This is kept separately because the published
+    /// pose has the root translation removed.
+    previous_root_motion_translation: Option<FGVec3>,
+    root_motion_delta: crate::math::vec3::FGVec3,
 }
 
 #[derive(Component, Clone, Debug, Default)]
@@ -111,7 +143,11 @@ impl FighterBoneMatrices {
         let Some(pose) = baked.sample_pose(frame) else {
             return false;
         };
-        self.set_pose(
+        self.set_pose_with_frame(
+            *frame,
+            "root",
+            FGVec3::ZERO,
+            None,
             frame.kind,
             &baked.bone_names,
             &baked.parents,
@@ -158,6 +194,11 @@ impl FighterBoneMatrices {
     pub fn get_current_index(&self, index: usize) -> Option<FixedMat4> {
         self.matrices.get(index).copied()
     }
+    /// Translation of the configured root-motion bone since the previous
+    /// simulation animation frame, in scaled model-space units.
+    pub fn root_motion_delta(&self) -> FGVec3 {
+        self.root_motion_delta
+    }
     pub fn iter(&self) -> impl Iterator<Item = (&str, FixedMat4)> {
         self.bone_names
             .iter()
@@ -180,6 +221,7 @@ impl FighterBoneMatrices {
             .unwrap_or(current);
         Some(interpolate_transform(previous, current, overstep_fraction))
     }
+    #[cfg(test)]
     pub(super) fn set_pose(
         &mut self,
         kind: AnimKind,
@@ -188,8 +230,44 @@ impl FighterBoneMatrices {
         local: &[FixedMat4],
         model_scale: FGi32,
     ) {
-        self.sample_pose(kind, bone_names, parents, local, model_scale, true);
+        self.set_pose_with_frame(
+            FighterAnimationFrame::new(kind, false),
+            "",
+            FGVec3::ZERO,
+            None,
+            kind,
+            bone_names,
+            parents,
+            local,
+            model_scale,
+        );
     }
+    pub(super) fn set_pose_with_frame(
+        &mut self,
+        animation_frame: FighterAnimationFrame,
+        root_motion_bone: &str,
+        root_motion_cycle_delta: FGVec3,
+        root_motion_loop_frame_count: Option<u32>,
+        kind: AnimKind,
+        bone_names: &[String],
+        parents: &[Option<usize>],
+        local: &[FixedMat4],
+        model_scale: FGi32,
+    ) {
+        self.sample_pose(
+            animation_frame,
+            root_motion_bone,
+            root_motion_cycle_delta,
+            root_motion_loop_frame_count,
+            kind,
+            bone_names,
+            parents,
+            local,
+            model_scale,
+            true,
+        );
+    }
+    #[cfg(test)]
     pub(super) fn resample_pose(
         &mut self,
         kind: AnimKind,
@@ -198,10 +276,49 @@ impl FighterBoneMatrices {
         local: &[FixedMat4],
         model_scale: FGi32,
     ) {
-        self.sample_pose(kind, bone_names, parents, local, model_scale, false);
+        self.resample_pose_with_frame(
+            FighterAnimationFrame::new(kind, false),
+            "",
+            FGVec3::ZERO,
+            None,
+            kind,
+            bone_names,
+            parents,
+            local,
+            model_scale,
+        );
+    }
+    pub(super) fn resample_pose_with_frame(
+        &mut self,
+        animation_frame: FighterAnimationFrame,
+        root_motion_bone: &str,
+        _root_motion_cycle_delta: FGVec3,
+        _root_motion_loop_frame_count: Option<u32>,
+        kind: AnimKind,
+        bone_names: &[String],
+        parents: &[Option<usize>],
+        local: &[FixedMat4],
+        model_scale: FGi32,
+    ) {
+        self.sample_pose(
+            animation_frame,
+            root_motion_bone,
+            FGVec3::ZERO,
+            None,
+            kind,
+            bone_names,
+            parents,
+            local,
+            model_scale,
+            false,
+        );
     }
     fn sample_pose(
         &mut self,
+        animation_frame: FighterAnimationFrame,
+        root_motion_bone: &str,
+        root_motion_cycle_delta: FGVec3,
+        root_motion_loop_frame_count: Option<u32>,
         kind: AnimKind,
         bone_names: &[String],
         parents: &[Option<usize>],
@@ -219,6 +336,7 @@ impl FighterBoneMatrices {
             parents.len(),
             "baked bone parents do not match names"
         );
+        let animation_changed = self.presentation_kind != Some(kind);
         if self.bone_names.is_empty() {
             self.bone_names.extend_from_slice(bone_names);
             self.parents.extend_from_slice(parents);
@@ -235,9 +353,19 @@ impl FighterBoneMatrices {
             std::mem::swap(&mut self.matrices, &mut self.previous_frame_matrices);
             std::mem::swap(&mut self.local_matrices, &mut self.previous_local_matrices);
         }
-        let animation_changed = self.presentation_kind != Some(kind);
         self.local_matrices.clear();
         self.local_matrices.extend_from_slice(local);
+
+        let root_index = if root_motion_bone.is_empty() {
+            None
+        } else {
+            Some(
+                self.bone_names
+                    .iter()
+                    .position(|name| name == root_motion_bone)
+                    .expect("configured root motion bone should exist"),
+            )
+        };
         self.model_matrices.resize(local.len(), None);
         self.model_matrices.fill(None);
         for index in 0..local.len() {
@@ -252,12 +380,57 @@ impl FighterBoneMatrices {
                 [FGi32::ZERO, FGi32::ZERO, FGi32::ZERO, FGi32::ONE],
             ],
         };
+        let raw_root_motion_translation = root_index.map(|root_index| {
+            model_scale
+                .mul(
+                    self.model_matrices[root_index]
+                        .expect("baked bone hierarchy should be valid"),
+                )
+                .get_translation()
+        });
+
+        // Gameplay owns the root's displacement.  Keep rotation and scale in
+        // the animation, but remove its translation before publishing the pose
+        // used by visuals and gameplay volumes.
+        if let Some(root_index) = root_index {
+            self.local_matrices[root_index].translate(FGVec3::ZERO);
+            self.model_matrices.fill(None);
+            for index in 0..local.len() {
+                resolve_model_transform(index, parents, &self.local_matrices, &mut self.model_matrices)
+                    .expect("baked bone hierarchy should be valid");
+            }
+        }
         self.matrices.clear();
         self.matrices.extend(
             self.model_matrices.iter().map(|matrix| {
                 model_scale.mul(matrix.expect("baked bone hierarchy should be valid"))
             }),
         );
+        self.root_motion_delta = if advance_history
+            && !animation_changed
+            && self.previous_animation_frame.is_some()
+            && let (Some(current), Some(previous)) = (
+                raw_root_motion_translation,
+                self.previous_root_motion_translation,
+            )
+        {
+            let mut delta = current - previous;
+            if animation_frame.repeat
+                && self.previous_animation_frame.is_some_and(|previous| {
+                    previous.frame.saturating_add(1) == animation_frame.frame
+                })
+                && root_motion_loop_frame_count == Some(animation_frame.frame)
+            {
+                delta = delta + root_motion_cycle_delta;
+            }
+            delta
+        } else {
+            FGVec3::ZERO
+        };
+        self.previous_root_motion_translation = raw_root_motion_translation;
+        if advance_history {
+            self.previous_animation_frame = Some(animation_frame);
+        }
         // A state transition is a discontinuity, not an animation frame to
         // interpolate from the previous clip.  Keep the presentation pose at
         // the new clip's first/current frame immediately.
@@ -344,8 +517,18 @@ fn sample_fighter_bone_matrices(
     let manifest = manifests
         .get(&fighter.manifest)
         .expect("fighter manifest should be loaded before the match starts");
+    let root_motion_cycle_delta = baked
+        .root_motion_cycle_delta(frame.kind, &manifest.root_motion_bone, manifest.model_scale)
+        .unwrap_or(FGVec3::ZERO);
+    let root_motion_loop_frame_count = baked
+        .frame_count(frame.kind)
+        .map(|count| count.saturating_sub(1).max(1));
     if advance_history {
-        matrices.set_pose(
+        matrices.set_pose_with_frame(
+            *frame,
+            &manifest.root_motion_bone,
+            root_motion_cycle_delta,
+            root_motion_loop_frame_count,
             frame.kind,
             &baked.bone_names,
             &baked.parents,
@@ -353,7 +536,11 @@ fn sample_fighter_bone_matrices(
             manifest.model_scale,
         );
     } else {
-        matrices.resample_pose(
+        matrices.resample_pose_with_frame(
+            *frame,
+            &manifest.root_motion_bone,
+            FGVec3::ZERO,
+            None,
             frame.kind,
             &baked.bone_names,
             &baked.parents,