Three.ez/InstancedMesh2 - Enhanced InstancedMesh with frustum culling, fast raycasting (BVH), sorting, visibility management, LOD and more

agargaro · August 15, 2024, 1:27pm

Three.ez - InstancedMesh2

Simplify your three.js application development with three.ez!

InstancedMesh2 is an alternative version of InstancedMesh that offers advantages:

frustum culling for each instance
sorting
visibility for each instance
each instance can have an object similar to Object3D to simplify its use
spatial indexing (BVH) for fast raycasting and frustum culling

import { InstancedMesh2 } from '@three.ez/instanced-mesh';

const myInstancedMesh = new InstancedMesh2(renderer, count, geometry, material);

myInstancedMesh.updateInstances((obj, index) => {
  obj.position.z = index;
  obj.rotateY(Math.PI);
});

myInstancedMesh.computeBVH();

This library has only one dependency: three.js r159+.

Live Examples

These examples use vite, and some mobile devices may run out of memory.

More examples will be added soon…

Frustum Culling

Avoiding rendering objects outside the camera frustum can drastically improve performance (especially for complex geometries).

Frustum culling by default is performed by iterating all instances, but it is possible to speed up this process by creating a spatial indexing data structure (BVH).

By default perObjectFrustumCulled is true.

Sorting

Sorting should be used to decrease overdraw and render transparent objects.

By default sortObjects is false.

import { createRadixSort } from '@three.ez/instanced-mesh';

myInstancedMesh.sortObjects = true;
myInstancedMesh.customSort = createRadixSort(myInstancedMesh);

Visibility

Set the visibility status of each instance like this:

myInstancedMesh.setVisibilityAt(false, 0);
myInstancedMesh.instances[0].visible = false; // if instances array is created

Instances Array

It is possible to create an array of InstancedEntity (Object3D-like) in order to easily change the visibility, apply transformations and add custom data to each instance, using more memory.

myInstancedMesh.createInstances((obj, index) => {
  obj.position.random();
});

myInstancedMesh.instances[0].visible = false;

myInstancedMesh.instances[1].userData = {};

myInstancedMesh.instances[2].position.random();
myInstancedMesh.instances[2].quaternion.random();
myInstancedMesh.instances[2].scale.random();
myInstancedMesh.instances[2].updateMatrix(); // necessary after transformations

myInstancedMesh.instances[3].rotateX(Math.PI);
myInstancedMesh.instances[3].updateMatrix(); // necessary after transformations

Spatial Indexing Data Structure (Dynamic BVH)

To speed up raycasting and frustum culling, a spatial indexing data structure can be created to contain the boundingBoxes of all instances.

This works very well if the instances are mostly static (updating a BVH can be expensive) and scattered in world space.

// call this function after all instances have been valued
myInstancedMesh.computeBVH({ margin: 0, highPrecision: false });

If all instances are static set the margin to 0.

Setting a margin makes BVH updating faster, but may make raycasting and frustum culling slightly slower.

Raycasting tips

If you are not using a BVH, you can set the raycastOnlyFrustum property to true to avoid iterating over all instances.

It’s also highly recommended to use three-mesh-bvh to create a geometry BVH.

API

InstancedMesh2

export type Entity<T> = InstancedEntity & T;
export type UpdateEntityCallback<T> = (obj: Entity<T>, index: number) => void;

export interface BVHParams {
    margin?: number;
    highPrecision?: boolean;
}

export declare class InstancedMesh2<TCustomData = {}, TGeometry extends BufferGeometry = BufferGeometry, TMaterial extends Material | Material[] = Material, TEventMap extends Object3DEventMap = Object3DEventMap> extends Mesh<TGeometry, TMaterial, TEventMap> {
    type: 'InstancedMesh2';
    isInstancedMesh2: true;
    instances: Entity<TCustomData>[];
    instanceIndex: GLInstancedBufferAttribute;
    matricesTexture: DataTexture;
    colorsTexture: DataTexture;
    morphTexture: DataTexture;
    boundingBox: Box3;
    boundingSphere: Sphere;
    instancesCount: number;
    bvh: InstancedMeshBVH;
    perObjectFrustumCulled: boolean;
    sortObjects: boolean;
    customSort: any;
    raycastOnlyFrustum: boolean;
    visibilityArray: boolean[];
    customDepthMaterial: MeshDepthMaterial;
    customDistanceMaterial: MeshDistanceMaterial;
    get count(): number;
    get maxCount(): number;
    get material(): TMaterial;
    set material(value: TMaterial);
    /** THIS MATERIAL AND GEOMETRY CANNOT BE SHARED */
    constructor(renderer: WebGLRenderer, count: number, geometry: TGeometry, material?: TMaterial);
    updateInstances(onUpdate: UpdateEntityCallback<Entity<TCustomData>>): void;
    createInstances(onInstanceCreation?: UpdateEntityCallback<Entity<TCustomData>>): void;
    computeBVH(config?: BVHParams): void;
    disposeBVH(): void;
    setMatrixAt(id: number, matrix: Matrix4): void;
    getMatrixAt(id: number, matrix?: Matrix4): Matrix4;
    setVisibilityAt(id: number, visible: boolean): void;
    getVisibilityAt(id: number): boolean;
    setColorAt(id: number, color: ColorRepresentation): void;
    getColorAt(id: number, color?: Color): Color;
    setUniformAt(id: number, name: string, value: UniformValue): void;
    getMorphAt(index: number, object: Mesh): void;
    setMorphAt(index: number, object: Mesh): void;
    raycast(raycaster: Raycaster, result: Intersection[]): void;
    computeBoundingBox(): void;
    computeBoundingSphere(): void;
    copy(source: InstancedMesh2, recursive?: boolean): this;
    dispose(): this;
}

InstancedEntity

export type UniformValueNoNumber = Vector2 | Vector3 | Vector4 | Matrix3 | Matrix4;
export type UniformValue = number | UniformValueNoNumber;

export declare class InstancedEntity {
    isInstanceEntity: true;
    readonly id: number;
    readonly owner: InstancedMesh2;
    position: Vector3;
    scale: Vector3;
    quaternion: Quaternion;
    get visible(): boolean;
    set visible(value: boolean);
    get color(): Color;
    set color(value: ColorRepresentation);
    get matrix(): Matrix4;
    get matrixWorld(): Matrix4;
    constructor(owner: InstancedMesh2<any, any, any>, index: number);
    updateMatrix(): void;
    setUniform(name: string, value: UniformValue): void;
    copyTo(target: Mesh): void;
    applyMatrix4(m: Matrix4): this;
    applyQuaternion(q: Quaternion): this;
    rotateOnAxis(axis: Vector3, angle: number): this;
    rotateOnWorldAxis(axis: Vector3, angle: number): this;
    rotateX(angle: number): this;
    rotateY(angle: number): this;
    rotateZ(angle: number): this;
    translateOnAxis(axis: Vector3, distance: number): this;
    translateX(distance: number): this;
    translateY(distance: number): this;
    translateZ(distance: number): this;
}

Utils

export declare function patchShader(shader: string): string;

export declare function createRadixSort(target: InstancedMesh2): typeof radixSort<InstancedRenderItem>;

export declare function createTexture_float(count: number): DataTexture;
export declare function createTexture_vec2(count: number): DataTexture;
export declare function createTexture_vec3(count: number): DataTexture;
export declare function createTexture_vec4(count: number): DataTexture;
export declare function createTexture_mat3(count: number): DataTexture;
export declare function createTexture_mat4(count: number): DataTexture;

How Does It Work?

It works similarly to BatchedMesh: matrices, colors, etc. are stored in Texture instead of InstancedAttribute.

The only InstancedAttribute is used to store the indices of the instances to be rendered.

If you create a custom material, you will need to use Texture instead of InstancedBufferAttribute (don’t worry, there are utility methods).

Installation

You can install it via npm using the following command:

npm install @three.ez/instanced-mesh

Or you can import it from CDN:

<script type="importmap">
{
  "imports": {
    "three": "https://cdn.jsdelivr.net/npm/three@0.167.0/build/three.module.js",
    "three/addons/": "https://cdn.jsdelivr.net/npm/three@0.167.0/examples/jsm/",
    "@three.ez/instanced-mesh": "https://cdn.jsdelivr.net/npm/@three.ez/instanced-mesh/index.js",
    "bvh.js": "https://cdn.jsdelivr.net/npm/bvh.js/index.js"
  }
}
</script>

Questions?

If you have questions or need assistance, you can ask on our discord server.

Future Work

LOD system
Remove renderer from constructor parameters

Like it?

If you find this project helpful, I would greatly appreciate it if you could leave a star on this repository!

This helps me know that you appreciate my work and encourages me to continue improving it.

Thank you so much for your support!

Special thanks to

References

PavelBoytchev · August 15, 2024, 1:37pm

So, you have your own implementation of BVH?

agargaro · August 15, 2024, 1:44pm

Yes but actually… I lied on readme (it uses also bvh.js package) have to fix it!

I created a separate package for BVH management with a generic implementation (no dependencies on three.js) so that it can be easily used with any application (it can be used also for BatchedMesh for example).

I will document that repository shortly as well; the usage is very simple. Here you can find how it is used in a wrapper (to handle frustum culling and raycasting):

github.com

three-ez/instanced-mesh/blob/e6c3bc14c0e68ca9889082ac54b3e7be36f62a58/src/objects/InstancedMeshBVH.ts

import { Box3, Matrix4, Raycaster } from 'three';
import { BVH, BVHNode, FloatArray, HybridBuilder, WebGLCoordinateSystem } from 'bvh.js';
import { InstancedMesh2 } from './InstancedMesh2.js';

type NodeData = {};
type LeafData = number; // instance id

export class InstancedMeshBVH {
    public target: InstancedMesh2;
    public geoBoundingBox: Box3;
    public bvh: BVH<NodeData, LeafData>;
    public map = new Map<number, BVHNode<NodeData, LeafData>>();
    protected _arrayType: typeof Float32Array | typeof Float64Array;

    constructor(target: InstancedMesh2<any, any, any>, margin = 0, highPrecision = false) {
        this.target = target;
        if (!target.geometry.boundingBox) target.geometry.computeBoundingBox();
        this.geoBoundingBox = target.geometry.boundingBox;
        this._arrayType = highPrecision ? Float64Array : Float32Array;
        this.bvh = new BVH(new HybridBuilder(margin), WebGLCoordinateSystem);

This file has been truncated. show original

manthrax · August 16, 2024, 5:51am

That 1m trees demo is sick.

agargaro · August 16, 2024, 1:45pm

Thank you sensei!

I will post an open world demo soon

agargaro · November 5, 2024, 10:10pm

I am finalizing the new feature: shadow LODs

Here is an example:

const boxGeo = new BoxGeometry(100, 1000, 100);
const trees = new InstancedMesh2(main.renderer, count, treeGLTF.geometry, treeGLTF.material);
trees.addLOD(boxGeo, new MeshLambertMaterial(), 100);
trees.addShadowLOD(trees.geometry);
trees.addShadowLOD(boxGeo, 50);

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