reflection-probe.js

const Signal = require('signals')
const mat4 = require('pex-math/mat4')
const hammersley = require('hammersley')

const FULLSCREEN_QUAD = require('./shaders/reflection-probe/fullscreen-quad.vert.js')

const CUBEMAP_TO_OCTMAP = require('./shaders/reflection-probe/cubemap-to-octmap.frag.js')
const CONVOLVE_OCT_MAP_ATLAS_TO_OCT_MAP = require('./shaders/reflection-probe/convolve-oct-map-atlas-to-oct-map.frag.js')
const BLIT_TO_OCT_MAP_ATLAS = require('./shaders/reflection-probe/blit-to-oct-map-atlas.frag.js')
const DOWNSAMPLE_FROM_OCT_MAP_ATLAS = require('./shaders/reflection-probe/downsample-from-oct-map-atlas.frag.js')
const PREFILTER_FROM_OCT_MAP_ATLAS = require('./shaders/reflection-probe/prefilter-from-oct-map-atlas.frag.js')

function ReflectionProbe(opts) {
  this.type = 'ReflectionProbe'
  this.enabled = true
  this.changed = new Signal()
  this.rgbm = false

  this.set(opts)

  const ctx = opts.ctx
  this._ctx = ctx
  this.dirty = true

  const CUBEMAP_SIZE = 512
  const dynamicCubemap = (this._dynamicCubemap = ctx.textureCube({
    width: CUBEMAP_SIZE,
    height: CUBEMAP_SIZE,
    pixelFormat: this.rgbm ? ctx.PixelFormat.RGBA8 : ctx.PixelFormat.RGBA16F,
    encoding: this.rgbm ? ctx.Encoding.RGBM : ctx.Encoding.Linear
  }))

  const sides = [
    { eye: [0, 0, 0], target: [1, 0, 0], up: [0, -1, 0] },
    { eye: [0, 0, 0], target: [-1, 0, 0], up: [0, -1, 0] },
    { eye: [0, 0, 0], target: [0, 1, 0], up: [0, 0, 1] },
    { eye: [0, 0, 0], target: [0, -1, 0], up: [0, 0, -1] },
    { eye: [0, 0, 0], target: [0, 0, 1], up: [0, -1, 0] },
    { eye: [0, 0, 0], target: [0, 0, -1], up: [0, -1, 0] }
  ].map((side, i) => {
    side.projectionMatrix = mat4.perspective(
      mat4.create(),
      Math.PI / 2,
      1,
      0.1,
      100
    ) // TODO: change this to radians
    side.viewMatrix = mat4.lookAt(mat4.create(), side.eye, side.target, side.up)
    side.drawPassCmd = {
      name: 'ReflectionProbe.sidePass',
      pass: ctx.pass({
        name: 'ReflectionProbe.sidePass',
        color: [
          {
            texture: dynamicCubemap,
            target: ctx.gl.TEXTURE_CUBE_MAP_POSITIVE_X + i
          }
        ],
        clearColor: [0, 0, 0, 1],
        clearDepth: 1
      })
    }
    return side
  })
  const quadPositions = [[-1, -1], [1, -1], [1, 1], [-1, 1]]
  const quadTexCoords = [[0, 0], [1, 0], [1, 1], [0, 1]]
  const quadFaces = [[0, 1, 2], [0, 2, 3]]
  const attributes = {
    aPosition: ctx.vertexBuffer(quadPositions),
    aTexCoord: ctx.vertexBuffer(quadTexCoords)
  }

  const indices = ctx.indexBuffer(quadFaces)

  const octMap = (this._octMap = ctx.texture2D({
    width: 1024,
    height: 1024,
    pixelFormat: this.rgbm ? ctx.PixelFormat.RGBA8 : ctx.PixelFormat.RGBA16F,
    encoding: this.rgbm ? ctx.Encoding.RGBM : ctx.Encoding.Linear
  }))

  const irradianceOctMapSize = 64

  const octMapAtlas = (this._reflectionMap = ctx.texture2D({
    width: 2 * 1024,
    height: 2 * 1024,
    min: ctx.Filter.Linear,
    mag: ctx.Filter.Linear,
    pixelFormat: this.rgbm ? ctx.PixelFormat.RGBA8 : ctx.PixelFormat.RGBA16F,
    encoding: this.rgbm ? ctx.Encoding.RGBM : ctx.Encoding.Linear
  }))

  const cubemapToOctMap = {
    name: 'ReflectionProbe.cubemapToOctMap',
    pass: ctx.pass({
      name: 'ReflectionProbe.cubemapToOctMap',
      color: [octMap]
    }),
    pipeline: ctx.pipeline({
      vert: FULLSCREEN_QUAD,
      frag: CUBEMAP_TO_OCTMAP
    }),
    attributes: attributes,
    indices: indices,
    uniforms: {
      uTextureSize: octMap.width,
      uCubemap: dynamicCubemap
    }
  }

  const convolveOctmapAtlasToOctMap = {
    name: 'ReflectionProbe.convolveOctmapAtlasToOctMap',
    pass: ctx.pass({
      name: 'ReflectionProbe.convolveOctmapAtlasToOctMap',
      color: [octMap]
    }),
    pipeline: ctx.pipeline({
      vert: FULLSCREEN_QUAD,
      frag: CONVOLVE_OCT_MAP_ATLAS_TO_OCT_MAP
    }),
    attributes: attributes,
    indices: indices,
    uniforms: {
      uTextureSize: irradianceOctMapSize,
      uSource: octMapAtlas,
      uSourceSize: octMapAtlas.width,
      uSourceEncoding: octMapAtlas.encoding,
      uOutputEncoding: octMap.encoding
    }
  }

  const clearOctMapAtlasCmd = {
    name: 'ReflectionProbe.clearOctMapAtlas',
    pass: ctx.pass({
      name: 'ReflectionProbe.clearOctMapAtlas',
      color: [octMapAtlas],
      clearColor: [0, 0, 0, 0]
    })
  }

  const blitToOctMapAtlasCmd = {
    name: 'ReflectionProbe.blitToOctMapAtlasCmd',
    pass: ctx.pass({
      name: 'ReflectionProbe.blitToOctMapAtlasCmd',
      color: [octMapAtlas]
    }),
    pipeline: ctx.pipeline({
      vert: FULLSCREEN_QUAD,
      frag: BLIT_TO_OCT_MAP_ATLAS
    }),
    uniforms: {
      uSource: octMap,
      uSourceSize: octMap.width
    },
    attributes: attributes,
    indices: indices
  }

  const downsampleFromOctMapAtlasCmd = {
    name: 'ReflectionProbe.downsampleFromOctMapAtlasCmd',
    pass: ctx.pass({
      name: 'ReflectionProbe.downsampleFromOctMapAtlasCmd',
      color: [octMap],
      clearColor: [0, 1, 0, 1]
    }),
    pipeline: ctx.pipeline({
      vert: FULLSCREEN_QUAD,
      frag: DOWNSAMPLE_FROM_OCT_MAP_ATLAS
    }),
    uniforms: {
      uSource: octMapAtlas,
      uSourceSize: octMapAtlas.width
    },
    attributes: attributes,
    indices: indices
  }

  const prefilterFromOctMapAtlasCmd = {
    name: 'ReflectionProbe.prefilterFromOctMapAtlasCmd',
    pass: ctx.pass({
      name: 'ReflectionProbe.prefilterFromOctMapAtlasCmd',
      color: [octMap],
      clearColor: [0, 1, 0, 1]
    }),
    pipeline: ctx.pipeline({
      vert: FULLSCREEN_QUAD,
      frag: PREFILTER_FROM_OCT_MAP_ATLAS
    }),
    uniforms: {
      uSource: octMapAtlas,
      uSourceSize: octMapAtlas.width,
      uSourceEncoding: octMapAtlas.encoding,
      uOutputEncoding: octMap.encoding
    },
    attributes: attributes,
    indices: indices
  }

  const numSamples = 128
  const hammersleyPointSet = new Float32Array(4 * numSamples)
  for (let i = 0; i < numSamples; i++) {
    const p = hammersley(i, numSamples)
    hammersleyPointSet[i * 4] = p[0]
    hammersleyPointSet[i * 4 + 1] = p[1]
    hammersleyPointSet[i * 4 + 2] = 0
    hammersleyPointSet[i * 4 + 3] = 0
  }

  const hammersleyPointSetMap = ctx.texture2D({
    data: hammersleyPointSet,
    width: 1,
    height: numSamples,
    pixelFormat: ctx.PixelFormat.RGBA32F,
    encoding: ctx.Encoding.Linear
  })

  function blitToOctMapAtlasLevel(
    mipmapLevel,
    roughnessLevel,
    sourceRegionSize
  ) {
    const width = octMapAtlas.width
    const levelSize = Math.max(
      64,
      width / (2 << (mipmapLevel + roughnessLevel))
    )
    const roughnessLevelWidth = width / (2 << roughnessLevel)
    const vOffset = width - Math.pow(2, Math.log2(width) - roughnessLevel)
    const hOffset =
      2 * roughnessLevelWidth -
      Math.pow(2, Math.log2(2 * roughnessLevelWidth) - mipmapLevel)
    ctx.submit(blitToOctMapAtlasCmd, {
      viewport: [hOffset, vOffset, levelSize, levelSize],
      uniforms: {
        uLevelSize: levelSize,
        uSourceRegionSize: sourceRegionSize
      }
    })
  }

  function downsampleFromOctMapAtlasLevel(
    mipmapLevel,
    roughnessLevel,
    targetRegionSize
  ) {
    ctx.submit(downsampleFromOctMapAtlasCmd, {
      viewport: [0, 0, targetRegionSize, targetRegionSize],
      uniforms: {
        uMipmapLevel: mipmapLevel,
        uRoughnessLevel: roughnessLevel
      }
    })
  }

  function prefilterFromOctMapAtlasLevel(
    sourceMipmapLevel,
    sourceRoughnessLevel,
    roughnessLevel,
    targetRegionSize
  ) {
    ctx.submit(prefilterFromOctMapAtlasCmd, {
      viewport: [0, 0, targetRegionSize, targetRegionSize],
      uniforms: {
        uSourceMipmapLevel: sourceMipmapLevel,
        uSourceRoughnessLevel: sourceRoughnessLevel,
        uRoughnessLevel: roughnessLevel,
        uNumSamples: numSamples,
        uHammersleyPointSetMap: hammersleyPointSetMap
      }
    })
  }

  this.update = function(drawScene) {
    if (!drawScene) return
    this.dirty = false

    sides.forEach((side) => {
      ctx.submit(side.drawPassCmd, () =>
        drawScene(side, dynamicCubemap.encoding)
      )
    })

    ctx.submit(cubemapToOctMap)

    ctx.submit(clearOctMapAtlasCmd)

    // mipmap levels go horizontally
    // roughness levels go vertically

    const maxLevel = 5
    blitToOctMapAtlasLevel(0, 0, octMap.width)

    for (let i = 0; i < maxLevel - 1; i++) {
      downsampleFromOctMapAtlasLevel(i, 0, octMap.width / Math.pow(2, i + 1))
      blitToOctMapAtlasLevel(i + 1, 0, octMap.width / Math.pow(2, 1 + i))
    }
    blitToOctMapAtlasLevel(maxLevel, 0, 64)

    for (let i = 1; i <= maxLevel; i++) {
      // prefilterFromOctMapAtlasLevel(i, 0, i, Math.max(64, octMap.width / Math.pow(2, i + 1)))
      prefilterFromOctMapAtlasLevel(
        0,
        Math.max(0, i - 1),
        i,
        Math.max(64, octMap.width / Math.pow(2, i + 1))
      )
      blitToOctMapAtlasLevel(
        0,
        i,
        Math.max(64, octMap.width / Math.pow(2, 1 + i))
      )
    }

    ctx.submit(convolveOctmapAtlasToOctMap, {
      viewport: [0, 0, irradianceOctMapSize, irradianceOctMapSize]
    })

    ctx.submit(blitToOctMapAtlasCmd, {
      viewport: [
        octMapAtlas.width - irradianceOctMapSize,
        octMapAtlas.height - irradianceOctMapSize,
        irradianceOctMapSize,
        irradianceOctMapSize
      ],
      uniforms: {
        uSourceRegionSize: irradianceOctMapSize
      }
    })
  }
}

ReflectionProbe.prototype.init = function(entity) {
  this.entity = entity
}

ReflectionProbe.prototype.set = function(opts) {
  Object.assign(this, opts)
  Object.keys(opts).forEach((prop) => this.changed.dispatch(prop))
}

module.exports = function(opts) {
  return new ReflectionProbe(opts)
}