gpu-curtains/dist/esm/core/shaders/chunks/utils/BRDF_GGX.mjs

gpu-curtains is a 3D WebGPU rendering engine. It can be used as a standalone 3D engine, but also includes extra classes focused on mapping 3d objects to DOM elements; It allows users to synchronize values such as position, sizing, or scale between them.

const BRDF_GGX = (
  /* wgsl */
  `
fn DistributionGGX(NdotH: f32, roughness: f32) -> f32 {
  let a: f32 = pow2( roughness );
  let a2: f32 = pow2( a );

  let denom: f32 = (pow2( NdotH ) * (a2 - 1.0) + 1.0);

  return RECIPROCAL_PI * a2 / ( pow2( denom ) );
}

fn GeometrySmith(NdotL: f32, NdotV: f32, roughness: f32) -> f32 {
  let a: f32 = pow2( roughness );
  let a2: f32 = pow2( a );
  
  let gv: f32 = NdotL * sqrt( a2 + ( 1.0 - a2 ) * pow2( NdotV ) );
  let gl: f32 = NdotV * sqrt( a2 + ( 1.0 - a2 ) * pow2( NdotL ) );

  return 0.5 / max( gv + gl, EPSILON );
}

fn BRDF_GGX(
  NdotV: f32,
  NdotL: f32,
  NdotH: f32,
  VdotH: f32,
  roughness: f32,
  specularFactor: f32,
  specularColor: vec3f
) -> vec3f {
  // cook-torrance brdf
  let G: f32 = GeometrySmith(NdotL, NdotV, roughness);
  let D: f32 = DistributionGGX(NdotH, roughness);
  let F: vec3f = F_Schlick(specularColor, specularFactor, VdotH);
  
  return G * D * F;
}
`
);

export { BRDF_GGX };