From 9b3eccd29462859b8f201a1c0b5806f821316439 Mon Sep 17 00:00:00 2001
From: Victor Giers <mail@victorgiers.com>
Date: Sat, 2 May 2026 04:52:21 +0200
Subject: [PATCH] auto-git:  [add] src/foliage/foliage-render-batches.ts

---
 src/foliage/foliage-render-batches.ts | 151 ++++++++++++++++++++++++++
 1 file changed, 151 insertions(+)
 create mode 100644 src/foliage/foliage-render-batches.ts

diff --git a/src/foliage/foliage-render-batches.ts b/src/foliage/foliage-render-batches.ts
new file mode 100644
index 00000000..0938e92a
--- /dev/null
+++ b/src/foliage/foliage-render-batches.ts
@@ -0,0 +1,151 @@
+import { Matrix4, Quaternion, Vector3 } from "three";
+
+import type { Vec3 } from "../core/vector";
+import type { FoliagePrototype, FoliagePrototypeRegistry } from "./foliage";
+import type {
+  DerivedFoliageInstance,
+  FoliageScatterResult
+} from "./foliage-scatter";
+
+export const FOLIAGE_RENDER_LOD_LEVEL = 0 as const;
+
+export interface FoliageRenderBatch {
+  key: string;
+  terrainId: string;
+  layerId: string;
+  prototypeId: string;
+  lodLevel: typeof FOLIAGE_RENDER_LOD_LEVEL;
+  bundledPath: string;
+  castShadow: boolean;
+  instances: DerivedFoliageInstance[];
+}
+
+const IDENTITY_SOURCE_MATRIX = new Matrix4();
+const UP_VECTOR = new Vector3(0, 1, 0);
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.min(max, Math.max(min, value));
+}
+
+function createVector3(vector: Vec3): Vector3 {
+  return new Vector3(vector.x, vector.y, vector.z);
+}
+
+export function getFoliagePrototypeRenderLod(
+  prototype: FoliagePrototype
+): {
+  bundledPath: string;
+  castShadow: boolean;
+} | null {
+  const lod = prototype.lods.find(
+    (candidate) => candidate.level === FOLIAGE_RENDER_LOD_LEVEL
+  );
+
+  if (lod === undefined || lod.source !== "bundled") {
+    return null;
+  }
+
+  return {
+    bundledPath: lod.bundledPath,
+    castShadow: lod.castShadow
+  };
+}
+
+export function createFoliageRenderBatchKey(options: {
+  terrainId: string;
+  layerId: string;
+  prototypeId: string;
+  bundledPath: string;
+}): string {
+  return [
+    options.terrainId,
+    options.layerId,
+    options.prototypeId,
+    FOLIAGE_RENDER_LOD_LEVEL,
+    options.bundledPath
+  ].join("|");
+}
+
+export function createFoliageRenderBatches(
+  scatter: FoliageScatterResult,
+  prototypeRegistry: FoliagePrototypeRegistry
+): FoliageRenderBatch[] {
+  const batches = new Map<string, FoliageRenderBatch>();
+
+  for (const chunk of scatter.chunks) {
+    for (const instance of chunk.instances) {
+      const prototype = prototypeRegistry[instance.prototypeId];
+
+      if (prototype === undefined) {
+        continue;
+      }
+
+      const renderLod = getFoliagePrototypeRenderLod(prototype);
+
+      if (renderLod === null) {
+        continue;
+      }
+
+      const key = createFoliageRenderBatchKey({
+        terrainId: instance.terrainId,
+        layerId: instance.layerId,
+        prototypeId: instance.prototypeId,
+        bundledPath: renderLod.bundledPath
+      });
+      let batch = batches.get(key);
+
+      if (batch === undefined) {
+        batch = {
+          key,
+          terrainId: instance.terrainId,
+          layerId: instance.layerId,
+          prototypeId: instance.prototypeId,
+          lodLevel: FOLIAGE_RENDER_LOD_LEVEL,
+          bundledPath: renderLod.bundledPath,
+          castShadow: renderLod.castShadow,
+          instances: []
+        };
+        batches.set(key, batch);
+      }
+
+      batch.instances.push(instance);
+    }
+  }
+
+  return [...batches.values()].sort((left, right) =>
+    left.key.localeCompare(right.key)
+  );
+}
+
+export function createFoliageInstanceMatrix(
+  instance: Pick<
+    DerivedFoliageInstance,
+    "position" | "normal" | "yawRadians" | "scale" | "alignToNormal"
+  >,
+  sourceMatrix: Matrix4 = IDENTITY_SOURCE_MATRIX
+): Matrix4 {
+  const normal = createVector3(instance.normal);
+
+  if (normal.lengthSq() <= 0) {
+    normal.copy(UP_VECTOR);
+  } else {
+    normal.normalize();
+  }
+
+  const tilt = new Quaternion().setFromUnitVectors(UP_VECTOR, normal);
+  const tiltAmount = clamp(instance.alignToNormal, 0, 1);
+  const partialTilt = new Quaternion().slerpQuaternions(
+    new Quaternion(),
+    tilt,
+    tiltAmount
+  );
+  const yaw = new Quaternion().setFromAxisAngle(normal, instance.yawRadians);
+  const rotation = yaw.multiply(partialTilt);
+  const instanceMatrix = new Matrix4().compose(
+    createVector3(instance.position),
+    rotation,
+    new Vector3(instance.scale, instance.scale, instance.scale)
+  );
+
+  return instanceMatrix.multiply(sourceMatrix);
+}