npm package: @querielo/batched-mesh-extensions
Description: Utility extension methods for BatchedMesh
Author: Andrea Gargaro
Latest version: 0.0.12

<div align="center">
  
  <h1>Three.ez - BatchedMesh extensions</h1>
  <p>
    <em>Simplify your <b>three.js</b> application development with <b>three.ez</b>!</em> <br><br>
    <b><a href="https://github.com/agargaro/instanced-mesh">three.ez/instanced-mesh</a></b> - Enhanced <code>InstancedMesh</code> with features for performance and usability
  </p>

  <br>

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This library adds and overrides some `BatchedMesh` methods to improve performance and add new features.

```ts
// Extends BatchedMesh prototype with new methods
extendBatchedMeshPrototype();

// Calculate the number of vertices and indices for a BatchedMesh and create it
const { vertexCount, indexCount } = getBatchedMeshCount(geometries);
const myBatchedMesh = new BatchedMesh(instanceCount, vertexCount, indexCount, material);

// Add geometries
const geoId = myBatchedMesh.addGeometry(geometries[geometryIndex]);

// Add instances
const instanceId = myBatchedMesh.addInstance(geoId);

// Compute the BVH to accelerate raycasting and frustum culling after adding all instances
myBatchedMesh.computeBVH();
```

- [**Spatial indexing (dynamic BVH)**](#spatial-indexing-dynamic-bvh): *speed up raycasting and frustum culling.*
- [**Per-instance uniforms**](#per-instance-uniforms-webglrenderer-only): *assign unique shader data to individual instances.*
- [**Level of Detail (LOD)**](#level-of-detail-lod): *dynamically adjust instance detail based on distance.*

## Live Examples

**Using three.js vanilla**

- Will be added in the future. Or you consider to contribute with a PR.

**Using three.ez/main (WebGLRenderer)**

- [Custom uniforms per instance](https://stackblitz.com/edit/three-ez-batchedmesh-extensions?file=src%2Fmain.ts)
- [Compute a BVH](https://glitch.com/edit/#!/three-ez-batched-mesh-extensions-bvh)
- [Compute a BVH and use three-mesh-bvh](https://glitch.com/edit/#!/three-ez-batched-mesh-extensions-three-mesh-bvh?path=main.js)
- [LOD](https://glitch.com/edit/#!/three-ez-batched-mesh-extensions-lod?path=main.js)

## Need help?

Join us on [Discord](https://discord.gg/MVTwrdX3JM) or open an issue on GitHub.

## Like it?

If you like this project, please leave a star. Thank you! ❤️

## Documentation

The documentation is available [here](https://agargaro.github.io/batched-mesh-extensions).

## Installation

You can install it via npm using the following command:

```bash
npm install @three.ez/batched-mesh-extensions
```

Or you can import it from CDN:

### WebGLRenderer

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

### WebGPURenderer

```html
<script type="importmap">
{
  "imports": {
    "three": "https://cdn.jsdelivr.net/npm/three/build/three.webgpu.js",
    "three/addons/": "https://cdn.jsdelivr.net/npm/three/examples/jsm/",
    "@three.ez/batched-mesh-extensions": "https://cdn.jsdelivr.net/npm/@three.ez/batched-mesh-extensions/build/webgpu.js",
    "bvh.js": "https://cdn.jsdelivr.net/npm/bvh.js/build/index.js",
  }
}
</script>
```

## Extend BatchedMesh prototype

To extend the `BatchedMesh` prototype with the new methods, you need to call the `extendBatchedMeshPrototype()` method at the top of your application.

```ts
import { extendBatchedMeshPrototype } from '@three.ez/batched-mesh-extensions';

extendBatchedMeshPrototype();
```

For more advanced use, it's also possible to manually update the `BatchedMesh` prototype because the new methods are all exported.

## Features

### Spatial indexing (dynamic BVH)

**To speed up raycasting and frustum culling**, a spatial indexing data structure can be created to contain the bounding boxes of all instances. <br>
This works very well if the instances are **mostly static** (updating a BVH can be expensive) and scattered in world space. <br>

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

```ts
myBatchedMesh.computeBVH(renderer.coordinateSystem, { margin: 0 }); // margin is optional
```

**It's necessary to manually update the BVH after its creation with the following methods:**

```ts
myBatchedMesh.bvh.insert(instanceId);
myBatchedMesh.bvh.insertRange(instanceIdsArray);
myBatchedMesh.bvh.move(instanceId);
myBatchedMesh.bvh.delete(instanceId);
myBatchedMesh.bvh.clear();
```

### Per-instance uniforms

Assign unique shader uniforms to each instance, working with every materials.

```ts
myBatchedMesh.initUniformsPerInstance({ vertex: { noise: 'float' }, fragment: { metalness: 'float', roughness: 'float', emissive: 'vec3' } });

myBatchedMesh.setUniformAt(index, 'noise', 0.5);
myBatchedMesh.setUniformAt(index, 'emissive', new Color('red'));
```

### Level of Detail (LOD)

Improve rendering performance by dynamically adjusting the detail level of instances based on their distance from the camera. <br>
Use simplified geometries for distant objects to optimize resources.

Currently, only LODs that share the same geometry vertex array can be added. This will improve in the future.

```ts
const geometryId = batchedMesh.addGeometry(geometry, -1, reservedIndexCount);
batchedMesh.addGeometryLOD(geometryId, geometryLOD1, distanceLOD1);
batchedMesh.addGeometryLOD(geometryId, geometryLOD2, distanceLOD2);
batchedMesh.addGeometryLOD(geometryId, geometryLOD3, distanceLOD3);
```  

## Special thanks to

- [gkjohnson](https://github.com/gkjohnson)
- [manthrax](https://github.com/manthrax)
- [donmccurdy](https://github.com/donmccurdy)  
- [ctrlmonster](https://github.com/Ctrlmonster)