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ProjectorLightNode: Fix back-projection. #31473

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Merged
Mugen87 merged 2 commits into from
Jul 22, 2025
Merged

ProjectorLightNode: Fix back-projection. #31473

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12964ce
ProjectorLightNode: Fix back-projection.
Mugen87 Jul 22, 2025
e5c213c
ProjectorLightNode: Clean up.
Mugen87 Jul 22, 2025
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ProjectorLightNode: Fix back-projection.
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@Mugen87
Mugen87 committed Jul 22, 2025
commit 12964ce630d5098953265acecbaba16ded09d2c2
23 changes: 17 additions & 6 deletions src/nodes/lighting/ProjectorLightNode.js
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Original file line number Diff line number Diff line change
@@ -1,8 +1,10 @@
import SpotLightNode from './SpotLightNode.js';

import { Fn, vec2 } from '../tsl/TSLCore.js';
import { float, Fn, If, vec2 } from '../tsl/TSLCore.js';
import { length, min, max, saturate, acos } from '../math/MathNode.js';
import { div, sub } from '../math/OperatorNode.js';
import { lightShadowMatrix } from '../accessors/Lights.js';
import { positionWorld } from '../accessors/Position.js';

const sdBox = /*@__PURE__*/ Fn( ( [ p, b ] ) => {

Expand Down Expand Up @@ -62,12 +64,21 @@ class ProjectorLightNode extends SpotLightNode {
getSpotAttenuation( builder ) {

const penumbraCos = this.penumbraCosNode;
const spotLightCoord = this.getLightCoord( builder );
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const coord = spotLightCoord.xyz.div( spotLightCoord.w );
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const spotLightCoord = lightShadowMatrix( this.light ).mul( builder.context.positionWorld || positionWorld );

const boxDist = sdBox( coord.xy.sub( vec2( 0.5 ) ), vec2( 0.5 ) );
const angleFactor = div( - 1.0, sub( 1.0, acos( penumbraCos ) ).sub( 1.0 ) );
const attenuation = saturate( boxDist.mul( - 2.0 ).mul( angleFactor ) );
const attenuation = float( 0 ).toVar( 'attenuation' );

// the sign of w determines whether the current fragment is in front or behind the light
// to avoid a back-projection, it's important to only compute an attenuation if w is positive

If( spotLightCoord.w.greaterThan( 0 ), () => {

const projectionUV = spotLightCoord.xyz.div( spotLightCoord.w );
const boxDist = sdBox( projectionUV.xy.sub( vec2( 0.5 ) ), vec2( 0.5 ) );
const angleFactor = div( - 1.0, sub( 1.0, acos( penumbraCos ) ).sub( 1.0 ) );
attenuation.assign( saturate( boxDist.mul( - 2.0 ).mul( angleFactor ) ) );

} );

return attenuation;

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