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23 lines
786 B
23 lines
786 B
2 years ago
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import {
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ShaderNode, div, max, sub, mul, clamp, pow, pow2, pow4, cond, greaterThan
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} from '../../shadernode/ShaderNodeBaseElements.js';
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const getDistanceAttenuation = new ShaderNode( ( inputs ) => {
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const { lightDistance, cutoffDistance, decayExponent } = inputs;
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// based upon Frostbite 3 Moving to Physically-based Rendering
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// page 32, equation 26: E[window1]
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// https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
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const distanceFalloff = div( 1.0, max( pow( lightDistance, decayExponent ), 0.01 ) );
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return cond(
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greaterThan( cutoffDistance, 0 ),
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mul( distanceFalloff, pow2( clamp( sub( 1.0, pow4( div( lightDistance, cutoffDistance ) ) ) ) ) ),
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distanceFalloff
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);
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} ); // validated
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export default getDistanceAttenuation;
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