gpu-curtains/dist/esm/core/shaders/chunks/fragment/head/get-PCF-point-shadow-contribution.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.

//#region src/core/shaders/chunks/fragment/head/get-PCF-point-shadow-contribution.ts
/** Helper chunk to get the PCF soft shadow generated by a given {@link core/lights/PointLight.PointLight | PointLight}. */
const getPCFPointShadowContribution = `
fn getPCFPointShadowContribution(index: i32, shadowPosition: vec4f, fragmentPosition: vec2f, depthCubeTexture: texture_depth_cube) -> f32 {
  let pointShadow: PointShadowsElement = pointShadows.pointShadowsElements[index];

  var visibility = 0.0;

  // for point lights, the uniform @vShadowCoord is re-purposed to hold
  // the vector from the light to the world-space position of the fragment.
  let lightToPosition: vec3f = shadowPosition.xyz;

  // For cube shadow maps, depth is stored as radial distance
  let distanceToLight: f32 = length(lightToPosition);

  if (distanceToLight < pointShadow.cameraNear || distanceToLight > pointShadow.cameraFar) {
    return 1.0;
  }

  // Direction from light to fragment
  // bd3D = base direction 3D
  let bd3D: vec3f = normalize(lightToPosition);

  let size: vec2u = textureDimensions(depthCubeTexture);
  let maxSize: f32 = f32(max(size.x, size.y));
  let texelSize: f32 = 1.0 / maxSize;

  // Hardware PCF with LinearFilter gives us 4-tap filtering per sample
  // 5 samples using Vogel disk + IGN = effectively 20 filtered taps with better distribution
  let radius: f32 = pointShadow.radius * texelSize;

  // Use IGN to rotate sampling pattern per pixel
  let phi: f32 = interleavedGradientNoise(fragmentPosition.xy) * PI2;

  var dp = (distanceToLight - pointShadow.cameraNear) / (pointShadow.cameraFar - pointShadow.cameraNear);
  dp = saturate(dp - pointShadow.bias);

  // Build a tangent-space coordinate system for applying offsets
  let absDir: vec3f = abs(bd3D);
  var tangent: vec3f = select(vec3(0.0, 1.0, 0.0), vec3(1.0, 0.0, 0.0), abs(bd3D.y) > 0.999);
  tangent = normalize(cross(bd3D, tangent));
  let bitangent: vec3f = cross(bd3D, tangent);

  let pcfSamples: i32 = pointShadow.pcfSamples;
  for(var i: i32 = 0; i < pcfSamples; i++) {
    let offset: vec2f = vogelDiskSample(i, pcfSamples, phi);
    let offsetDir: vec3f = tangent * offset.x + bitangent * offset.y;
    let sampleDir: vec3f = normalize(bd3D + offsetDir * radius);

    visibility += textureSampleCompareLevel(
        depthCubeTexture,
        depthComparisonSampler,
        sampleDir,
        dp
      );
  }

  visibility /= f32(pcfSamples);

  return mix(1.0, visibility, saturate(pointShadow.intensity));  
}`;
//#endregion
export { getPCFPointShadowContribution };