upadte: gain some fps

src/world/vegetation/VegetationSystem.tsx

@@ -1,6 +1,39 @@
 import { Suspense } from "react";
 import { InstancedVegetation } from "@/world/vegetation/InstancedVegetation";
-import { useVegetationData } from "@/world/vegetation/useVegetationData";
+import {
+  type VegetationInstance,
+  useVegetationData,
+} from "@/world/vegetation/useVegetationData";
+import {
+  INSTANCED_MAP_CHUNK_SIZE,
+  INSTANCED_MAP_NO_SHADOW_NAMES,
+} from "@/world/vegetation/vegetationConfig";
+
+function createChunkKey(instance: VegetationInstance): string {
+  const [x, , z] = instance.position;
+  const chunkX = Math.floor(x / INSTANCED_MAP_CHUNK_SIZE);
+  const chunkZ = Math.floor(z / INSTANCED_MAP_CHUNK_SIZE);
+  return `${chunkX}:${chunkZ}`;
+}
+
+function chunkInstances(
+  instances: VegetationInstance[],
+): Map<string, VegetationInstance[]> {
+  const chunks = new Map<string, VegetationInstance[]>();
+
+  for (const instance of instances) {
+    const key = createChunkKey(instance);
+    const chunk = chunks.get(key);
+
+    if (chunk) {
+      chunk.push(instance);
+    } else {
+      chunks.set(key, [instance]);
+    }
+  }
+
+  return chunks;
+}
 
 export function VegetationSystem(): React.JSX.Element | null {
   const { data, isLoading } = useVegetationData();
@@ -16,16 +49,20 @@ export function VegetationSystem(): React.JSX.Element | null {
           return null;
         }
 
-        return (
-          <Suspense key={modelName} fallback={null}>
+        const castShadow = !INSTANCED_MAP_NO_SHADOW_NAMES.has(modelName);
+        const receiveShadow = castShadow;
+        const chunks = chunkInstances(entry.instances);
+
+        return [...chunks.entries()].map(([chunkKey, instances]) => (
+          <Suspense key={`${modelName}:${chunkKey}`} fallback={null}>
             <InstancedVegetation
               modelPath={entry.modelPath}
-              instances={entry.instances}
-              castShadow={true}
-              receiveShadow={true}
+              instances={instances}
+              castShadow={castShadow}
+              receiveShadow={receiveShadow}
             />
           </Suspense>
-        );
+        ));
       })}
     </group>
   );

src/world/vegetation/vegetationConfig.ts

@@ -9,3 +9,14 @@ export const INSTANCED_MAP_EXCEPTIONS = new Set([
   "blocking",
   "terrain",
 ]);
+
+export const INSTANCED_MAP_CHUNK_SIZE = 45;
+
+export const INSTANCED_MAP_NO_SHADOW_NAMES = new Set([
+  "arbre",
+  "sapin",
+  "buisson",
+  "champdeble",
+  "champdesoja",
+  "champsdetournesol",
+]);