debug(map): add path surface sampling preview

src/world/paths/PathSystem.tsx

@@ -1,12 +1,16 @@
+import { useEffect, useRef } from "react";
+import * as THREE from "three";
 import { InstancedMapAsset } from "@/world/map-instancing/InstancedMapAsset";
 import {
-  PATH_SYSTEM_ENABLED,
+  PATH_DEBUG_PREVIEW_ENABLED,
+  PATH_TILE_RENDER_ENABLED,
   PATH_TILE_MODEL_PATH,
 } from "@/world/paths/pathConfig";
 import { usePathTileData } from "@/world/paths/usePathTileData";
+import type { MapAssetInstance } from "@/world/map-instancing/useMapInstancingData";
 
 export function PathSystem(): React.JSX.Element | null {
-  if (!PATH_SYSTEM_ENABLED) {
+  if (!PATH_DEBUG_PREVIEW_ENABLED && !PATH_TILE_RENDER_ENABLED) {
     return null;
   }
 
@@ -20,6 +24,14 @@ function PathTiles(): React.JSX.Element | null {
     return null;
   }
 
+  if (PATH_DEBUG_PREVIEW_ENABLED) {
+    return <PathDebugPreview instances={pathTiles} />;
+  }
+
+  if (!PATH_TILE_RENDER_ENABLED) {
+    return null;
+  }
+
   return (
     <InstancedMapAsset
       castShadow={false}
@@ -29,3 +41,43 @@ function PathTiles(): React.JSX.Element | null {
     />
   );
 }
+
+function PathDebugPreview({
+  instances,
+}: {
+  instances: MapAssetInstance[];
+}): React.JSX.Element {
+  const instancedMeshRef = useRef<THREE.InstancedMesh>(null);
+
+  useEffect(() => {
+    const instancedMesh = instancedMeshRef.current;
+    if (!instancedMesh) return;
+
+    const matrix = new THREE.Matrix4();
+    const position = new THREE.Vector3();
+    const quaternion = new THREE.Quaternion();
+    const scale = new THREE.Vector3(1, 1, 1);
+
+    for (let i = 0; i < instances.length; i++) {
+      const instance = instances[i];
+      if (!instance) continue;
+
+      position.set(instance.position[0], 0.08, instance.position[2]);
+      matrix.compose(position, quaternion, scale);
+      instancedMesh.setMatrixAt(i, matrix);
+    }
+
+    instancedMesh.instanceMatrix.needsUpdate = true;
+    instancedMesh.computeBoundingSphere();
+  }, [instances]);
+
+  return (
+    <instancedMesh
+      ref={instancedMeshRef}
+      args={[undefined, undefined, instances.length]}
+    >
+      <boxGeometry args={[0.35, 0.08, 0.35]} />
+      <meshBasicMaterial color="#ff00ff" />
+    </instancedMesh>
+  );
+}

src/world/paths/pathConfig.ts

@@ -1,7 +1,8 @@
 import { TERRAIN_COLORS, TERRAIN_TILE_SIZE } from "@/data/world/terrainConfig";
 
 export const PATH_SURFACE_KEY = "chemin";
-export const PATH_SYSTEM_ENABLED = false;
+export const PATH_DEBUG_PREVIEW_ENABLED = true;
+export const PATH_TILE_RENDER_ENABLED = false;
 export const PATH_TILE_MODEL_PATH = TERRAIN_COLORS.chemin.modelPath;
 export const PATH_TILE_SIZE =
   TERRAIN_COLORS.chemin.tileSize ?? TERRAIN_TILE_SIZE;