Update collision detection to handle triangle meshes and transformed colliders

src/runtime-three/runtime-host.js

@@ -592,19 +592,36 @@ export class RuntimeHost {
     }
     collectRuntimeStaticWaterContactPatches(brush) {
         const contactBounds = [];
-        for (const otherBrush of this.runtimeScene?.brushes ?? []) {
-            if (otherBrush.id === brush.id || otherBrush.volume.mode !== "none") {
+        const runtimeBrushesById = new Map((this.runtimeScene?.brushes ?? []).map((runtimeBrush) => [runtimeBrush.id, runtimeBrush]));
+        for (const collider of this.runtimeScene?.colliders ?? []) {
+            if (collider.source === "brush") {
+                const otherBrush = runtimeBrushesById.get(collider.brushId);
+                if (otherBrush === undefined || otherBrush.id === brush.id || otherBrush.volume.mode !== "none") {
+                    continue;
+                }
+                contactBounds.push({
+                    kind: "triangleMesh",
+                    vertices: collider.vertices,
+                    indices: collider.indices,
+                    transform: {
+                        position: collider.center,
+                        rotationDegrees: collider.rotationDegrees,
+                        scale: {
+                            x: 1,
+                            y: 1,
+                            z: 1
+                        }
+                    }
+                });
                 continue;
             }
-            contactBounds.push({
-                kind: "orientedBox",
-                center: otherBrush.center,
-                rotationDegrees: otherBrush.rotationDegrees,
-                size: otherBrush.size
-            });
-        }
-        for (const collider of this.runtimeScene?.colliders ?? []) {
-            if (collider.source !== "modelInstance") {
+            if (collider.kind === "trimesh") {
+                contactBounds.push({
+                    kind: "triangleMesh",
+                    vertices: collider.vertices,
+                    indices: collider.indices,
+                    transform: collider.transform
+                });
                 continue;
             }
             contactBounds.push({

src/runtime-three/runtime-host.ts

@@ -815,21 +815,40 @@ export class RuntimeHost {
   private collectRuntimeStaticWaterContactPatches(brush: RuntimeBoxBrushInstance) {
     const contactBounds: Parameters<typeof collectWaterContactPatches>[1] = [];
 
-    for (const otherBrush of this.runtimeScene?.brushes ?? []) {
-      if (otherBrush.id === brush.id || otherBrush.volume.mode !== "none") {
+    const runtimeBrushesById = new Map((this.runtimeScene?.brushes ?? []).map((runtimeBrush) => [runtimeBrush.id, runtimeBrush]));
+
+    for (const collider of this.runtimeScene?.colliders ?? []) {
+      if (collider.source === "brush") {
+        const otherBrush = runtimeBrushesById.get(collider.brushId);
+
+        if (otherBrush === undefined || otherBrush.id === brush.id || otherBrush.volume.mode !== "none") {
+          continue;
+        }
+
+        contactBounds.push({
+          kind: "triangleMesh",
+          vertices: collider.vertices,
+          indices: collider.indices,
+          transform: {
+            position: collider.center,
+            rotationDegrees: collider.rotationDegrees,
+            scale: {
+              x: 1,
+              y: 1,
+              z: 1
+            }
+          }
+        });
         continue;
       }
 
-      contactBounds.push({
-        kind: "orientedBox",
-        center: otherBrush.center,
-        rotationDegrees: otherBrush.rotationDegrees,
-        size: otherBrush.size
-      });
-    }
-
-    for (const collider of this.runtimeScene?.colliders ?? []) {
-      if (collider.source !== "modelInstance") {
+      if (collider.kind === "trimesh") {
+        contactBounds.push({
+          kind: "triangleMesh",
+          vertices: collider.vertices,
+          indices: collider.indices,
+          transform: collider.transform
+        });
         continue;
       }
 

src/viewport-three/viewport-host.js

@@ -2204,11 +2204,20 @@ export class ViewportHost {
             if (brush.id === excludedBrushId || brush.volume.mode !== "none") {
                 continue;
             }
+            const derivedMesh = buildBoxBrushDerivedMeshData(brush);
             contactBounds.push({
-                kind: "orientedBox",
-                center: brush.center,
-                rotationDegrees: brush.rotationDegrees,
-                size: brush.size
+                kind: "triangleMesh",
+                vertices: derivedMesh.colliderVertices,
+                indices: derivedMesh.colliderIndices,
+                transform: {
+                    position: brush.center,
+                    rotationDegrees: brush.rotationDegrees,
+                    scale: {
+                        x: 1,
+                        y: 1,
+                        z: 1
+                    }
+                }
             });
         }
         for (const modelInstance of getModelInstances(document.modelInstances)) {
@@ -2222,7 +2231,17 @@ export class ViewportHost {
             try {
                 const generatedCollider = buildGeneratedModelCollider(modelInstance, asset, this.loadedModelAssets[modelInstance.assetId]);
                 if (generatedCollider !== null) {
-                    contactBounds.push(generatedCollider.worldBounds);
+                    if (generatedCollider.kind === "trimesh") {
+                        contactBounds.push({
+                            kind: "triangleMesh",
+                            vertices: generatedCollider.vertices,
+                            indices: generatedCollider.indices,
+                            transform: generatedCollider.transform
+                        });
+                    }
+                    else {
+                        contactBounds.push(generatedCollider.worldBounds);
+                    }
                 }
             }
             catch {

src/viewport-three/viewport-host.ts

@@ -3013,11 +3013,21 @@ export class ViewportHost {
         continue;
       }
 
+      const derivedMesh = buildBoxBrushDerivedMeshData(brush);
+
       contactBounds.push({
-        kind: "orientedBox",
-        center: brush.center,
-        rotationDegrees: brush.rotationDegrees,
-        size: brush.size
+        kind: "triangleMesh",
+        vertices: derivedMesh.colliderVertices,
+        indices: derivedMesh.colliderIndices,
+        transform: {
+          position: brush.center,
+          rotationDegrees: brush.rotationDegrees,
+          scale: {
+            x: 1,
+            y: 1,
+            z: 1
+          }
+        }
       });
     }
 
@@ -3036,7 +3046,16 @@ export class ViewportHost {
         const generatedCollider = buildGeneratedModelCollider(modelInstance, asset, this.loadedModelAssets[modelInstance.assetId]);
 
         if (generatedCollider !== null) {
-          contactBounds.push(generatedCollider.worldBounds);
+          if (generatedCollider.kind === "trimesh") {
+            contactBounds.push({
+              kind: "triangleMesh",
+              vertices: generatedCollider.vertices,
+              indices: generatedCollider.indices,
+              transform: generatedCollider.transform
+            });
+          } else {
+            contactBounds.push(generatedCollider.worldBounds);
+          }
         }
       } catch {
         // Validation already surfaces unsupported collider modes; the viewport keeps rendering.

tests/domain/water-material.test.ts

@@ -220,6 +220,62 @@ describe("water material helpers", () => {
     expect(Math.abs(clippedPatch?.axisZ ?? 0)).toBeGreaterThan(0.65);
   });
 
+  it("builds contact patches for transformed triangle meshes that cross the water surface", () => {
+    const patches = collectWaterContactPatches(
+      {
+        center: {
+          x: 0,
+          y: 0,
+          z: 0
+        },
+        rotationDegrees: {
+          x: 0,
+          y: 0,
+          z: 0
+        },
+        size: {
+          x: 8,
+          y: 2,
+          z: 8
+        }
+      },
+      [
+        {
+          kind: "triangleMesh",
+          vertices: new Float32Array([
+            -1, 0, -1,
+            1, 0, -1,
+            1, 0, 1,
+            -1, 0, 1
+          ]),
+          indices: new Uint32Array([0, 1, 2, 0, 2, 3]),
+          transform: {
+            position: {
+              x: 0,
+              y: 1,
+              z: 0
+            },
+            rotationDegrees: {
+              x: 35,
+              y: 28,
+              z: 18
+            },
+            scale: {
+              x: 2,
+              y: 1,
+              z: 1.4
+            }
+          }
+        }
+      ]
+    );
+
+    expect(patches.length).toBeGreaterThan(0);
+    expect(patches[0]?.halfWidth ?? 0).toBeGreaterThan(0.2);
+    expect(Math.abs(patches[0]?.axisX ?? 0)).toBeGreaterThan(0.2);
+    expect(Math.abs(patches[0]?.axisZ ?? 0)).toBeGreaterThan(0.2);
+  });
+
   it("builds a shared quality shader material for visible tinted water", () => {
     const result = createWaterMaterial({
       colorHex: "#4da6d9",