auto-git:

[add] src/rendering/terrain-layer-material.ts
 [add] tests/domain/terrains.test.ts
 [change] src/app/App.tsx
 [change] src/core/terrain-brush.ts
 [change] src/document/migrate-scene-document.ts
 [change] src/document/scene-document-validation.ts
 [change] src/document/scene-document.ts
 [change] src/document/terrains.ts
 [change] src/geometry/terrain-brush.ts
 [change] src/geometry/terrain-mesh.ts
 [change] src/runtime-three/rapier-collision-world.ts
 [change] src/runtime-three/runtime-host.ts
 [change] src/runtime-three/runtime-scene-build.ts
 [change] src/viewport-three/ViewportCanvas.tsx
 [change] src/viewport-three/ViewportPanel.tsx
 [change] src/viewport-three/viewport-host.ts
 [change] tests/domain/build-runtime-scene.test.ts
 [change] tests/domain/rapier-collision-world.test.ts
 [change] tests/domain/terrain.command.test.ts
 [change] tests/domain/water-material.test.ts
 [change] tests/geometry/terrain-brush.test.ts
 [change] tests/geometry/terrain-mesh.test.ts
 [change] tests/serialization/scene-document-json.test.ts
 [change] tests/unit/terrain-foundation.integration.test.tsx
 [change] tests/unit/viewport-canvas.test.tsx

tests/geometry/terrain-mesh.test.ts

@@ -56,4 +56,46 @@ describe("terrain mesh generation", () => {
 
     expect(Array.from(derivedMesh.uvs)).toEqual([10, -6, 12, -6, 10, -4, 12, -4]);
   });
+
+  it("derives full per-vertex layer weights from the compact terrain paint data", () => {
+    const terrain = createTerrain({
+      sampleCountX: 2,
+      sampleCountZ: 2,
+      paintWeights: [
+        0.2,
+        0.3,
+        0.1,
+        0,
+        0.5,
+        0,
+        0.1,
+        0.1,
+        0.1,
+        0.25,
+        0.25,
+        0.25
+      ]
+    });
+
+    const derivedMesh = buildTerrainDerivedMeshData(terrain);
+
+    expect(Array.from(derivedMesh.layerWeights)).toEqual([
+      expect.closeTo(0.4, 5),
+      expect.closeTo(0.2, 5),
+      expect.closeTo(0.3, 5),
+      expect.closeTo(0.1, 5),
+      expect.closeTo(0.5, 5),
+      expect.closeTo(0, 5),
+      expect.closeTo(0.5, 5),
+      expect.closeTo(0, 5),
+      expect.closeTo(0.7, 5),
+      expect.closeTo(0.1, 5),
+      expect.closeTo(0.1, 5),
+      expect.closeTo(0.1, 5),
+      expect.closeTo(0.25, 5),
+      expect.closeTo(0.25, 5),
+      expect.closeTo(0.25, 5),
+      expect.closeTo(0.25, 5)
+    ]);
+  });
 });