Initial work on ledge & improved baking of root motion. (#90)

Reviewed-on: #90
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

src/stage/manifest.rs

@@ -9,7 +9,10 @@ use strum_macros::EnumIter;
 use crate::{
     AppState, game_settings::GameSettings, math::{vec::FGVec2}, stage::{
         StagePoly,
-        line::{StageCollision, StagePolyLineSegmentType, StagePolyType},
+        line::{
+            StageCollision, StageLedge, StageLedgeSide, StagePolyLineSegment,
+            StagePolyLineSegmentType, StagePolyType, StageVertexID,
+        },
     }, texture_reference::TextureReference,
 };
 use bevy::prelude::*;
@@ -71,6 +74,16 @@ pub enum StageId {
 pub struct StagePolyDefinition {
     poly_type: StagePolyType,
     lines: Vec<(FGVec2, StagePolyLineSegmentType)>,
+    #[serde(default)]
+    ledges: Vec<StageLedgeDefinition>,
+}
+
+#[derive(Serialize, Deserialize, Clone, Copy, Reflect)]
+pub struct StageLedgeDefinition {
+    /// Index into the polygon's `lines`, identifying the corner position.
+    vertex: usize,
+    /// Side of the corner on which a grabbing fighter will hang.
+    hang_side: StageLedgeSide,
 }
 
 #[derive(Deserialize, Clone, Asset, Reflect, RonAsset)]
@@ -176,6 +189,13 @@ pub fn prepare_stage_manifests(
             );
             return;
         }
+        if let Err(error) = manifest.validate_ledges() {
+            fail(
+                &mut next_state,
+                &format!("{:?} has invalid ledges: {error}", manifest.id),
+            );
+            return;
+        }
         if registry.insert(manifest.id, handle.clone()).is_some() {
             fail(
                 &mut next_state,
@@ -267,6 +287,14 @@ impl StageManifest {
         Ok(())
     }
 
+    fn validate_ledges(&self) -> Result<(), String> {
+        for (polygon_index, definition) in self.polygons.iter().enumerate() {
+            definition.validate_ledges(polygon_index)?;
+        }
+
+        Ok(())
+    }
+
     pub fn to_collision(&self) -> StageCollision {
         let stage_polys: Vec<StagePoly> = self
             .polygons
@@ -274,7 +302,84 @@ impl StageManifest {
             .map(|def| StagePoly::build(def.poly_type, &def.lines))
             .collect();
 
-        StageCollision { stage_polys }
+        let ledges = self
+            .polygons
+            .iter()
+            .enumerate()
+            .flat_map(|(polygon, definition)| definition.resolved_ledges(polygon))
+            .collect();
+
+        StageCollision {
+            stage_polys,
+            ledges,
+        }
+    }
+}
+
+impl StagePolyDefinition {
+    fn validate_ledges(&self, polygon_index: usize) -> Result<(), String> {
+        let polygon = StagePoly::build(self.poly_type, &self.lines);
+        let mut vertices = HashSet::with_capacity(self.ledges.len());
+
+        for ledge in &self.ledges {
+            if ledge.vertex >= self.lines.len() {
+                return Err(format!(
+                    "polygon {polygon_index} references missing vertex {}",
+                    ledge.vertex
+                ));
+            }
+            if !vertices.insert(ledge.vertex) {
+                return Err(format!(
+                    "polygon {polygon_index} defines vertex {} as a ledge more than once",
+                    ledge.vertex
+                ));
+            }
+
+            let outgoing = polygon.get_segment(ledge.vertex);
+            let incoming_index = if ledge.vertex > 0 {
+                Some(ledge.vertex - 1)
+            } else if matches!(self.poly_type, StagePolyType::Closed) {
+                polygon.segments.len().checked_sub(1)
+            } else {
+                None
+            };
+            let incoming = incoming_index.and_then(|index| polygon.get_segment(index));
+            let is_walkable_floor = |segment: Option<&StagePolyLineSegment>| {
+                segment.is_some_and(|segment| {
+                    segment.segment_type == StagePolyLineSegmentType::Floor
+                        && segment.normal.y > crate::math::int::FGi32::ZERO
+                })
+            };
+            let (interior, exterior) = match ledge.hang_side {
+                StageLedgeSide::Left => (outgoing, incoming),
+                StageLedgeSide::Right => (incoming, outgoing),
+            };
+            if !is_walkable_floor(interior) {
+                return Err(format!(
+                    "polygon {polygon_index} vertex {} has no upward-facing floor opposite its {:?} hang side",
+                    ledge.vertex, ledge.hang_side
+                ));
+            }
+            if is_walkable_floor(exterior) {
+                return Err(format!(
+                    "polygon {polygon_index} vertex {} is between two walkable floors rather than at an exposed corner",
+                    ledge.vertex
+                ));
+            }
+        }
+
+        Ok(())
+    }
+
+    fn resolved_ledges(&self, polygon: usize) -> impl Iterator<Item = StageLedge> + '_ {
+        self.ledges.iter().map(move |ledge| StageLedge {
+            id: StageVertexID {
+                polygon,
+                vertex: ledge.vertex,
+            },
+            position: self.lines[ledge.vertex].0,
+            hang_side: ledge.hang_side,
+        })
     }
 }
 
@@ -319,3 +424,85 @@ impl StageCameraProfile {
                 < 90.0
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn platform(ledges: Vec<StageLedgeDefinition>) -> StagePolyDefinition {
+        StagePolyDefinition {
+            poly_type: StagePolyType::Platform,
+            lines: vec![
+                (FGVec2::lit("-5", "0"), StagePolyLineSegmentType::Floor),
+                (FGVec2::lit("5", "0"), StagePolyLineSegmentType::Floor),
+            ],
+            ledges,
+        }
+    }
+
+    #[test]
+    fn platform_endpoints_can_be_defined_as_ledges() {
+        let definition = platform(vec![
+            StageLedgeDefinition {
+                vertex: 0,
+                hang_side: StageLedgeSide::Left,
+            },
+            StageLedgeDefinition {
+                vertex: 1,
+                hang_side: StageLedgeSide::Right,
+            },
+        ]);
+
+        assert_eq!(definition.validate_ledges(3), Ok(()));
+        let ledges = definition.resolved_ledges(3).collect::<Vec<_>>();
+        assert_eq!(ledges[0].id, StageVertexID { polygon: 3, vertex: 0 });
+        assert_eq!(ledges[0].position, FGVec2::lit("-5", "0"));
+        assert_eq!(ledges[1].id, StageVertexID { polygon: 3, vertex: 1 });
+        assert_eq!(ledges[1].position, FGVec2::lit("5", "0"));
+    }
+
+    #[test]
+    fn invalid_and_duplicate_ledge_vertices_are_rejected() {
+        let missing = platform(vec![StageLedgeDefinition {
+            vertex: 2,
+            hang_side: StageLedgeSide::Right,
+        }]);
+        assert!(missing.validate_ledges(0).is_err());
+
+        let duplicate = platform(vec![
+            StageLedgeDefinition {
+                vertex: 0,
+                hang_side: StageLedgeSide::Left,
+            },
+            StageLedgeDefinition {
+                vertex: 0,
+                hang_side: StageLedgeSide::Right,
+            },
+        ]);
+        assert!(duplicate.validate_ledges(0).is_err());
+    }
+
+    #[test]
+    fn ledge_must_border_an_upward_facing_floor() {
+        let definition = StagePolyDefinition {
+            poly_type: StagePolyType::Platform,
+            lines: vec![
+                (FGVec2::lit("0", "0"), StagePolyLineSegmentType::Wall),
+                (FGVec2::lit("0", "5"), StagePolyLineSegmentType::Wall),
+            ],
+            ledges: vec![StageLedgeDefinition {
+                vertex: 0,
+                hang_side: StageLedgeSide::Left,
+            }],
+        };
+
+        assert!(definition.validate_ledges(0).is_err());
+
+        let wrong_side = platform(vec![StageLedgeDefinition {
+            vertex: 0,
+            hang_side: StageLedgeSide::Right,
+        }]);
+        assert!(wrong_side.validate_ledges(0).is_err());
+    }
+
+}