LightUtils.js•1.12 kB
import { Fn } from '../tsl/TSLBase.js';
/** @module LightUtils **/
/**
* Represents a `discard` shader operation in TSL.
*
* @method
* @param {Object} inputs - The input parameter object.
* @param {Node<float>} inputs.lightDistance - The distance of the light's position to the current fragment position.
* @param {Node<float>} inputs.cutoffDistance - The light's cutoff distance.
* @param {Node<float>} inputs.decayExponent - The light's decay exponent.
* @return {Node<float>} The distance falloff.
*/
export const getDistanceAttenuation = /*@__PURE__*/ Fn( ( inputs ) => {
const { lightDistance, cutoffDistance, decayExponent } = inputs;
// based upon Frostbite 3 Moving to Physically-based Rendering
// page 32, equation 26: E[window1]
// https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
const distanceFalloff = lightDistance.pow( decayExponent ).max( 0.01 ).reciprocal();
return cutoffDistance.greaterThan( 0 ).select(
distanceFalloff.mul( lightDistance.div( cutoffDistance ).pow4().oneMinus().clamp().pow2() ),
distanceFalloff
);
} ); // validated