WebGPUPathTracer: Adjust PCG random usage in Wavefront Path Tracer

src/webgpu/compute/wavefront/ProcessHitsKernel.js

@@ -6,6 +6,7 @@ import { queuedRayStruct, queuedHitStruct } from './structs.js';
 import { proxy, proxyFn } from '../../lib/nodes/NodeProxy.js';
 import { weightedAlphaBlendFn } from '../../nodes/sampling.wgsl.js';
 import { wgslTagFn } from '../../lib/nodes/WGSLTagFnNode.js';
+import { getPcgSeed, setPcgSeed } from '../../nodes/random.wgsl.js';
 
 export class ProcessHitsKernel extends ComputeKernel {
 
@@ -27,8 +28,8 @@ export class ProcessHitsKernel extends ComputeKernel {
 			hitQueue: storage( new IndirectStorageBufferAttribute( 1, queuedHitStruct.getLength() ), queuedHitStruct ),
 			queueSizes: storage( new IndirectStorageBufferAttribute( 4, 1 ), 'u32' ).toAtomic(),
 
-			textures: texture( new DataTexture( ) ),
-			textureSampler: sampler( new DataTexture( ) ),
+			textures: texture( new DataTexture() ),
+			textureSampler: sampler( new DataTexture() ),
 
 			globalId: globalId,
 		};
@@ -69,7 +70,7 @@ export class ProcessHitsKernel extends ComputeKernel {
 				let input = hitQueue[ hitIndex ];
 				let indexUV = vec2u( input.pixel_x, input.pixel_y );
 
-				g_state.s0 = input.pcgStateS0;
+				${ setPcgSeed }( input.pcgStateS0 );
 
 				let object = transforms[ input.objectIndex ];
 				var material = materials[ object.materialIndex ];
@@ -105,7 +106,7 @@ export class ProcessHitsKernel extends ComputeKernel {
 					rayQueue[ index ].pixel = indexUV;
 					rayQueue[ index ].throughputColor = input.throughputColor * scatterRec.color / scatterRec.pdf;
 					rayQueue[ index ].currentBounce = input.currentBounce + 1;
-					rayQueue[ index ].pcgStateS0 = g_state.s0;
+					rayQueue[ index ].pcgStateS0 = ${ getPcgSeed }();
 					rayQueue[ index ].resultColor = resultColor;
 
 				}

src/webgpu/compute/wavefront/RayGenerationKernel.js

@@ -3,7 +3,7 @@ import { IndirectStorageBufferAttribute, StorageTexture } from 'three/webgpu';
 import { uniform, storage, globalId, textureStore } from 'three/tsl';
 import { ComputeKernel } from '../ComputeKernel.js';
 import { ndcToCameraRay } from '../../lib/wgsl/common.wgsl.js';
-import { pcgInit, pcgRand2 } from '../../nodes/random.wgsl.js';
+import { getPcgSeed, pcgInit, pcgRand2 } from '../../nodes/random.wgsl.js';
 import { queuedRayStruct } from './structs.js';
 import { wgslTagFn } from '../../lib/nodes/WGSLTagFnNode.js';
 
@@ -92,7 +92,7 @@ export class RayGenerationKernel extends ComputeKernel {
 				rayQueue[ index ].pixel = indexUV;
 				rayQueue[ index ].throughputColor = vec3f( 1.0 );
 				rayQueue[ index ].currentBounce = 0;
-				rayQueue[ index ].pcgStateS0 = g_state.s0;
+				rayQueue[ index ].pcgStateS0 = ${ getPcgSeed }();
 				rayQueue[ index ].resultColor = vec4f( 0.0, 0.0, 0.0, 1.0 );
 
 				// write the active params

src/webgpu/compute/wavefront/RayIntersectionKernel.js

@@ -1,7 +1,7 @@
 import { DataTexture, Matrix3, IndirectStorageBufferAttribute, StorageTexture } from 'three/webgpu';
 import { ComputeKernel } from '../ComputeKernel.js';
 import { uniform, texture, sampler, storage, textureStore, globalId } from 'three/tsl';
-import { pcgRand2, pcgInit } from '../../nodes/random.wgsl.js';
+import { pcgRand2, setPcgSeed } from '../../nodes/random.wgsl.js';
 import { queuedRayStruct, queuedHitStruct } from './structs.js';
 import { proxy } from '../../lib/nodes/NodeProxy.js';
 import { sampleEnvironmentFn, weightedAlphaBlendFn } from '../../nodes/sampling.wgsl.js';
@@ -90,7 +90,7 @@ export class RayIntersectionKernel extends ComputeKernel {
 				let indexUV = input.pixel;
 				let seed = ( textureLoad( ${ params.sampleCountTarget }, indexUV ).r & ( ~ ACTIVE_FLAG ) ) + input.currentBounce;
 
-				${ pcgInit }( indexUV, seed );
+				${ setPcgSeed }( input.pcgStateS0 );
 
 				// run intersection
 				let ray = Ray( input.origin, input.direction );

src/webgpu/nodes/random.wgsl.js

@@ -22,6 +22,18 @@ export const pcgInit = wgslFn( /* wgsl */`
 	}
 `, [ pcgStateStruct ] );
 
+export const getPcgSeed = wgslFn( /* wgsl */`
+	fn pcgGetSeed() -> vec4u {
+		return g_state.s0;
+	}
+`, [ pcgStateStruct ] );
+
+export const setPcgSeed = wgslFn( /* wgsl */`
+	fn pcgSetSeed( s0: vec4u ) -> void {
+		g_state.s0 = s0;
+	}
+`, [ pcgStateStruct ] );
+
 export const pcg4d = wgslFn( /* wgsl */ `
 	fn pcg4d(v: ptr<private, vec4u>) -> void {
 		*v = *v * 1664525u + 1013904223u;
@@ -31,13 +43,6 @@ export const pcg4d = wgslFn( /* wgsl */ `
 	}
 ` );
 
-export const pcgCycleState = wgslFn( /* wgsl */ `
-	fn pcgCycleState(n: u32) -> void {
-		for (var i = 0u; i < n; i++) {
-			pcg4d(&g_state.s0);
-		}
-` );
-
 export const pcgRand = wgslFn( /*wgsl*/`
 	fn pcgRand() -> f32 {
 		pcg4d(&g_state.s0);