gpu-curtains/dist/esm/core/shaders/chunks/fragment/body/get-anisotropy.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.

import { getTextureSample } from "./get-texture-sample.mjs";
//#region src/core/shaders/chunks/fragment/body/get-anisotropy.ts
/**
* Set the `anisotropy` (`f32`), `anisotropyVector` (`vec2f`), as well as `alphaT` (`f32`), `anisotropyT` (`vec3f`) and `anisotropyB` (`vec3f`) values from the material anisotropy variables, `TBN` matrix and eventual anisotropy texture.
*
* @param parameters - Parameters used to set the anisotropy values.
* @param parameters.extensionsUsed - {@link PBRFragmentShaderInputParams.extensionsUsed | extensionsUsed} to check if anisotropy is enabled.
* @param parameters.anisotropyTexture - {@link ShaderTextureDescriptor | Anisotropy texture descriptor} (using the `RGB` channel) to use if any. `R` and `G` channels represent the anisotropy direction in `[-1, 1]` tangent, bitangent space to be rotated by the anisotropy rotation. The `B` channel contains strength as `[0, 1]` to be multiplied by the `anisotropy`.
* @returns - String with the `anisotropy` (`f32`), `anisotropyVector` (`vec2f`), as well as `alphaT` (`f32`), `anisotropyT` (`vec3f`) and `anisotropyB` (`vec3f`) values set.
*/
const getAnisotropy = ({ extensionsUsed = [], anisotropyTexture = null } = {}) => {
	let anisotropy = `
  var anisotropyT: vec3f = vec3(0.0);
  var anisotropyB: vec3f = vec3(0.0);
  var alphaT: f32 = 0.0;
  anisotropyVector *= anisotropy;
  `;
	if (extensionsUsed.includes("KHR_materials_anisotropy")) {
		if (anisotropyTexture) {
			anisotropy += getTextureSample(anisotropyTexture, "anisotropy");
			anisotropy += `
  let anisotropyMat: mat2x2f = mat2x2f(anisotropyVector.x, anisotropyVector.y, - anisotropyVector.y, anisotropyVector.x);
  anisotropyVector = anisotropyMat * normalize( 2.0 * anisotropySample.rg - vec2( 1.0 ) ) * anisotropySample.b;`;
		}
		anisotropy += `
  anisotropy = length( anisotropyVector );

  if( anisotropy == 0.0 ) {
    anisotropyVector = vec2( 1.0, 0.0 );
  } else {
    anisotropyVector /= anisotropy;
    anisotropy = saturate( anisotropy );
  }

  alphaT = mix( pow2( roughness ), 1.0, pow2( anisotropy ) );
  
  anisotropyT = tbn[ 0 ] * anisotropyVector.x + tbn[ 1 ] * anisotropyVector.y;
  anisotropyB = tbn[ 1 ] * anisotropyVector.x - tbn[ 0 ] * anisotropyVector.y;
  `;
	}
	return anisotropy;
};
//#endregion
export { getAnisotropy };