// lib/post/webgl/bloom.ts
// Bloom — spreads light from bright pixels for a soft glow. Wraps three's
// official UnrealBloomPass (multi-scale gaussian downsample/upsample).
// Mirrors the WebGPU `lib/post/webgpu/bloom.ts` effect.

import * as THREE from 'three'
import { UnrealBloomPass } from 'three/addons/postprocessing/UnrealBloomPass.js'
import type { Pass } from 'three/addons/postprocessing/Pass.js'


export interface BloomOptions {
  strength?:  number
  radius?:    number
  threshold?: number
  width?:     number
  height?:    number
}

export function createBloom (options: BloomOptions = {}): Pass {
  const { strength = 0.7, radius = 0.4, threshold = 0.85, width = 1, height = 1 } = options
  const resolution                                                                = new THREE.Vector2(width, height)
  const pass                                                                      = new UnrealBloomPass(resolution, strength, radius, threshold)
  // resize later with `pass.setSize(w, h)` once the canvas dimensions are known.
  return pass
}

// perf: medium. Multi-pass downsample/upsample blur at reduced resolution.