sort

gistfile1.txt

import { Vector3, Camera } from 'three'

class IndexedVector3 extends Vector3 {
  constructor(public readonly index: number, public bufferIndex: number = -1) {
    super()
  }
}

export class ParticleSorter {
  private _currentBuffer: number[] = []
  private _pool: IndexedVector3[] = []
  private _deadVectors: number[] = []
  private _liveVectors: Map<IndexedVector3, boolean> = new Map()
  private _list: IndexedVector3[] = []
  private _liveParticles = 0

  receive(positionBuffer: Float32Array, liveParticleCount: number) {
    for (let i = 0; i < liveParticleCount; i++) {
      const i3 = i * 3
      const i4 = i * 4
      for (let j = 0; j < 3; j++) {
        this._currentBuffer[i3 + j] = positionBuffer[i4 + j]
      }
    }
    this._liveParticles = liveParticleCount
  }

  sortBuffer(camera: Camera) {
    this._releaseAll()
    this._list = []

    for (let i = 0; i < this._liveParticles; i++) {
      const v = this._getVector()
      v.bufferIndex = i
      let i3 = i * 3
      v.set(
        this._currentBuffer[i3++],
        this._currentBuffer[i3++],
        this._currentBuffer[i3++]
      )
      v.applyMatrix4(camera.matrixWorldInverse)
      this._list.push(v)
    }

    this._list.sort((a, b) => a.z - b.z)
    // console.log(this._list)
    const indecis: number[] = this._list.map(v => v.bufferIndex)
    return indecis
  }

  private _getVector() {
    let v
    if (this._deadVectors.length) {
      v = this._pool[this._deadVectors.pop()!].set(0, 0, 0)
    } else {
      v = new IndexedVector3(this._pool.length)
      this._pool.push(v)
    }
    this._liveVectors.set(v, true)
    return v
  }
  private _releaseVector(v: IndexedVector3) {
    this._deadVectors.push(v.index)
    this._liveVectors.delete(v)
  }
  private _releaseAll() {
    this._liveVectors.forEach((_, v) => {
      this._releaseVector(v)
    })
  }
}