ShadowFilterNode: Use textureGatherCompare in PCFSoftShadowFilter (#33534)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Shota Matsuda <shota@takram.com>

src/nodes/lighting/ShadowFilterNode.js

@@ -1,4 +1,4 @@
-import { float, vec2, vec4, If, Fn } from '../tsl/TSLBase.js';
+import { float, vec2, vec4, If, Fn, ivec2 } from '../tsl/TSLBase.js';
 import { reference } from '../accessors/ReferenceNode.js';
 import { texture } from '../accessors/TextureNode.js';
 import { mix, fract, step, max, clamp } from '../math/MathNode.js';
@@ -97,69 +97,38 @@ export const PCFShadowFilter = /*@__PURE__*/ Fn( ( { depthTexture, shadowCoord,
  */
 export const PCFSoftShadowFilter = /*@__PURE__*/ Fn( ( { depthTexture, shadowCoord, shadow, depthLayer } ) => {
 
-	const depthCompare = ( uv, compare ) => {
+	const mapSize = reference( 'mapSize', 'vec2', shadow ).setGroup( renderGroup );
 
-		let depth = texture( depthTexture, uv );
+	const texelSize = vec2( 1 ).div( mapSize );
 
-		if ( depthTexture.isArrayTexture ) {
+	const uv = shadowCoord.xy;
+	const f = fract( uv.mul( mapSize ).add( 0.5 ) ).toConst();
+	uv.subAssign( f.sub( 0.5 ).mul( texelSize ) );
 
-			depth = depth.depth( depthLayer );
+	const gatherCompare = ( offset ) => {
 
-		}
+		let t = texture( depthTexture, uv ).offset( offset ).gather();
 
-		return depth.compare( compare );
+		if ( depthTexture.isArrayTexture ) {
 
-	};
+			t = t.depth( depthLayer );
 
+		}
 
-	const mapSize = reference( 'mapSize', 'vec2', shadow ).setGroup( renderGroup );
+		return t.compare( shadowCoord.z );
 
-	const texelSize = vec2( 1 ).div( mapSize );
-	const dx = texelSize.x;
-	const dy = texelSize.y;
+	};
 
-	const uv = shadowCoord.xy;
-	const f = fract( uv.mul( mapSize ).add( 0.5 ) );
-	uv.subAssign( f.mul( texelSize ) );
+	const c1 = gatherCompare( ivec2( - 1, 1 ) ).toConst();
+	const c2 = gatherCompare( ivec2( 1, 1 ) ).toConst();
+	const c3 = gatherCompare( ivec2( - 1, - 1 ) ).toConst();
+	const c4 = gatherCompare( ivec2( 1, - 1 ) ).toConst();
 
 	return add(
-		depthCompare( uv, shadowCoord.z ),
-		depthCompare( uv.add( vec2( dx, 0 ) ), shadowCoord.z ),
-		depthCompare( uv.add( vec2( 0, dy ) ), shadowCoord.z ),
-		depthCompare( uv.add( texelSize ), shadowCoord.z ),
-		mix(
-			depthCompare( uv.add( vec2( dx.negate(), 0 ) ), shadowCoord.z ),
-			depthCompare( uv.add( vec2( dx.mul( 2 ), 0 ) ), shadowCoord.z ),
-			f.x
-		),
-		mix(
-			depthCompare( uv.add( vec2( dx.negate(), dy ) ), shadowCoord.z ),
-			depthCompare( uv.add( vec2( dx.mul( 2 ), dy ) ), shadowCoord.z ),
-			f.x
-		),
-		mix(
-			depthCompare( uv.add( vec2( 0, dy.negate() ) ), shadowCoord.z ),
-			depthCompare( uv.add( vec2( 0, dy.mul( 2 ) ) ), shadowCoord.z ),
-			f.y
-		),
-		mix(
-			depthCompare( uv.add( vec2( dx, dy.negate() ) ), shadowCoord.z ),
-			depthCompare( uv.add( vec2( dx, dy.mul( 2 ) ) ), shadowCoord.z ),
-			f.y
-		),
-		mix(
-			mix(
-				depthCompare( uv.add( vec2( dx.negate(), dy.negate() ) ), shadowCoord.z ),
-				depthCompare( uv.add( vec2( dx.mul( 2 ), dy.negate() ) ), shadowCoord.z ),
-				f.x
-			),
-			mix(
-				depthCompare( uv.add( vec2( dx.negate(), dy.mul( 2 ) ) ), shadowCoord.z ),
-				depthCompare( uv.add( vec2( dx.mul( 2 ), dy.mul( 2 ) ) ), shadowCoord.z ),
-				f.x
-			),
-			f.y
-		)
+		mix( c1.x, c2.y, f.x ).add( c1.y ).add( c2.x ).mul( f.y ),
+		mix( c1.w, c2.z, f.x ).add( c1.z ).add( c2.w ),
+		mix( c3.x, c4.y, f.x ).add( c3.y ).add( c4.x ),
+		mix( c3.w, c4.z, f.x ).add( c3.z ).add( c4.w ).mul( f.y.oneMinus() )
 	).mul( 1 / 9 );
 
 } );