SSGINode: Loop over horizon directions.

Inlines the sampling loop once instead of twice which reduces the
generated shader size by about a third.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

examples/jsm/tsl/display/SSGINode.js

@@ -1,5 +1,5 @@
 import { HalfFloatType, RenderTarget, Vector2, TempNode, QuadMesh, NodeMaterial, RendererUtils, MathUtils } from 'three/webgpu';
-import { clamp, normalize, reference, Fn, NodeUpdateType, uniform, vec4, passTexture, uv, logarithmicDepthToViewZ, viewZToPerspectiveDepth, getViewPosition, screenCoordinate, float, sub, fract, dot, vec2, rand, vec3, Loop, mul, PI, cos, sin, uint, cross, acos, sign, pow, luminance, If, max, abs, Break, sqrt, HALF_PI, div, ceil, shiftRight, convertToTexture, bool, getNormalFromDepth, countOneBits, interleavedGradientNoise } from 'three/tsl';
+import { clamp, normalize, reference, Fn, NodeUpdateType, uniform, vec4, passTexture, uv, logarithmicDepthToViewZ, viewZToPerspectiveDepth, getViewPosition, screenCoordinate, float, sub, fract, dot, vec2, rand, vec3, Loop, mul, PI, cos, sin, uint, cross, acos, sign, pow, luminance, If, max, abs, Break, sqrt, HALF_PI, div, ceil, shiftRight, convertToTexture, getNormalFromDepth, countOneBits, interleavedGradientNoise } from 'three/tsl';
 
 const _quadMesh = /*@__PURE__*/ new QuadMesh();
 const _size = /*@__PURE__*/ new Vector2();
@@ -578,8 +578,13 @@ class SSGINode extends TempNode {
 
 				globalOccludedBitfield.assign( 0 );
 
-				color.addAssign( horizonSampling( bool( true ), stepRadius, radiusVS, viewPosition, slideDirTexelSize, initialRayStep, uvNode, viewDir, viewNormal, n ) );
-				color.addAssign( horizonSampling( bool( false ), stepRadius, radiusVS, viewPosition, slideDirTexelSize, initialRayStep, uvNode, viewDir, viewNormal, n ) );
+				Loop( { start: uint( 0 ), end: uint( 2 ), type: 'uint', condition: '<', name: 'side' }, ( { side } ) => {
+
+					const directionIsRight = side.equal( uint( 0 ) );
+
+					color.addAssign( horizonSampling( directionIsRight, stepRadius, radiusVS, viewPosition, slideDirTexelSize, initialRayStep, uvNode, viewDir, viewNormal, n ) );
+
+				} );
 
 				ao.addAssign( float( countOneBits( globalOccludedBitfield ) ).div( float( MAX_RAY ) ) );