BatchedGeometry

[takahirox]

Related issue: #22376

Description

This PR adds BatchedGeometry to addons.

BatchedGeometry allows to render many dynamic and different shape object referring to the same material with a single draw call. Please read #22376 (comment) for basic concept in more details.

Demo: https://raw.githack.com/takahirox/three.js/BatchedGeometry/examples/index.html#webgl_geometry_batch

API

// Initialize
const geometry = new BatchedGeometry(maxVertexCount, maxIndexCount);
const ids = [];

for (let i = 0; i < geometries.length; i++) {
  const id = geometry.apply(geometries[i]);
  geometry.setMatrixAt(id, matrices[i]);
  ids.push(id);
}

const mesh = new THREE.Mesh(geometry, material);

// update
for (let i = 0; i < ids.length; i++) {
  const id = ids[i];
  geometry.getMatrixAt(id, matrix);
  // update translate/quaternion/scale here
  geometry.setMatrixAt(id, matrix);
}

[takahirox]

Closing because I realized that updating positions/normals in CPU and/or uploading attribute arrays are slow and BatchedGeometry is useless.

It seems that matrices must be applied in shader (GPU) for the performance. The geometry level API doesn't really fit for it then I made another PR with mesh level API #25059