@needle-tools/engine/src/engine/engine_instancing.ts

Needle Engine is a web-based runtime for 3D apps. It runs on your machine for development with great integrations into editors like Unity or Blender - and can be deployed onto any device! It is flexible, extensible and networking and XR are built-in.

import { InstancedMesh, Object3D } from "three";

export const NEED_UPDATE_INSTANCE_KEY = Symbol("NEEDLE_NEED_UPDATE_INSTANCE");

export const $isUsingInstancing = Symbol("isUsingInstancing");
export const $instancingRenderer = Symbol("instancingRenderer");
export const $instancingAutoUpdateBounds = Symbol("instancingAutoUpdateBounds");

/**
 * Utility class for accessing instancing related properties
 */
export class InstancingUtil {

    /** Is this object rendered using a InstancedMesh */
    static isUsingInstancing(instance: Object3D): boolean { return instance[$isUsingInstancing] === true; }
    /** Returns the instanced mesh IF the object is rendered by an instanced mesh
     * @link https://threejs.org/docs/#api/en/objects/InstancedMesh
     */
    static getRenderer(instance: Object3D): InstancedMesh | null { return instance[$instancingRenderer] || null; }

    setAutoUpdateBounds(instance: Object3D, value: boolean) {
        const renderer = InstancingUtil.getRenderer(instance);
        if (renderer) {
            renderer[$instancingAutoUpdateBounds] = value;
        }
    }


    // TODO: change this so it does not set matrix world directly but some flag that is only used by instancing
    /** Mark an instanced object dirty so the instance matrix will be updated */
    static markDirty(go: Object3D | null, recursive: boolean = true) {
        if (!go) return;
        // potential optimization:
        // if(go.matrixWorldNeedsUpdate) return;
        // console.warn("UPDATE", go);
        if (this.isUsingInstancing(go)) {
            go[NEED_UPDATE_INSTANCE_KEY] = true;
            go.matrixWorldNeedsUpdate = true;
        }
        if (recursive) {
            for (const child of go.children) {
                InstancingUtil.markDirty(child, true);
            }
        }
    }
}