@openhps/core/dist/esm/three/nodes/functions/BSDF/BRDF_Sheen.js

Open Hybrid Positioning System - Core component

import { transformedNormalView } from '../../accessors/Normal.js';
import { positionViewDirection } from '../../accessors/Position.js';
import { sheen, sheenRoughness } from '../../core/PropertyNode.js';
import { Fn, float } from '../../tsl/TSLBase.js';

// https://github.com/google/filament/blob/master/shaders/src/brdf.fs
const D_Charlie = /*@__PURE__*/Fn(({
  roughness,
  dotNH
}) => {
  const alpha = roughness.pow2();

  // Estevez and Kulla 2017, "Production Friendly Microfacet Sheen BRDF"
  const invAlpha = float(1.0).div(alpha);
  const cos2h = dotNH.pow2();
  const sin2h = cos2h.oneMinus().max(0.0078125); // 2^(-14/2), so sin2h^2 > 0 in fp16

  return float(2.0).add(invAlpha).mul(sin2h.pow(invAlpha.mul(0.5))).div(2.0 * Math.PI);
}).setLayout({
  name: 'D_Charlie',
  type: 'float',
  inputs: [{
    name: 'roughness',
    type: 'float'
  }, {
    name: 'dotNH',
    type: 'float'
  }]
});

// https://github.com/google/filament/blob/master/shaders/src/brdf.fs
const V_Neubelt = /*@__PURE__*/Fn(({
  dotNV,
  dotNL
}) => {
  // Neubelt and Pettineo 2013, "Crafting a Next-gen Material Pipeline for The Order: 1886"
  return float(1.0).div(float(4.0).mul(dotNL.add(dotNV).sub(dotNL.mul(dotNV))));
}).setLayout({
  name: 'V_Neubelt',
  type: 'float',
  inputs: [{
    name: 'dotNV',
    type: 'float'
  }, {
    name: 'dotNL',
    type: 'float'
  }]
});
const BRDF_Sheen = /*@__PURE__*/Fn(({
  lightDirection
}) => {
  const halfDir = lightDirection.add(positionViewDirection).normalize();
  const dotNL = transformedNormalView.dot(lightDirection).clamp();
  const dotNV = transformedNormalView.dot(positionViewDirection).clamp();
  const dotNH = transformedNormalView.dot(halfDir).clamp();
  const D = D_Charlie({
    roughness: sheenRoughness,
    dotNH
  });
  const V = V_Neubelt({
    dotNV,
    dotNL
  });
  return sheen.mul(D).mul(V);
});
export default BRDF_Sheen;