WebGPUBackend: Align frontFace and cullMode values to WebGL backend. (#31769)

src/renderers/webgpu/WebGPUBackend.js

@@ -1806,6 +1806,11 @@ class WebGPUBackend extends Backend {
 		const utils = this.utils;
 		const renderContext = renderObject.context;
 
+		// meshes with negative scale have a different frontFace render pipeline
+		// descriptor value so the following must be honored in the cache key
+
+		const frontFaceCW = ( object.isMesh && object.matrixWorld.determinant() < 0 );
+
 		return [
 			material.transparent, material.blending, material.premultipliedAlpha,
 			material.blendSrc, material.blendDst, material.blendEquation,
@@ -1816,6 +1821,7 @@ class WebGPUBackend extends Backend {
 			material.stencilFail, material.stencilZFail, material.stencilZPass,
 			material.stencilFuncMask, material.stencilWriteMask,
 			material.side,
+			frontFaceCW,
 			utils.getSampleCountRenderContext( renderContext ),
 			utils.getCurrentColorSpace( renderContext ), utils.getCurrentColorFormat( renderContext ), utils.getCurrentDepthStencilFormat( renderContext ),
 			utils.getPrimitiveTopology( object, material ),

src/renderers/webgpu/utils/WebGPUPipelineUtils.js

@@ -5,7 +5,7 @@ import {
 } from './WebGPUConstants.js';
 
 import {
-	FrontSide, BackSide, DoubleSide,
+	BackSide, DoubleSide,
 	NeverDepth, AlwaysDepth, LessDepth, LessEqualDepth, EqualDepth, GreaterEqualDepth, GreaterDepth, NotEqualDepth,
 	NoBlending, NormalBlending, AdditiveBlending, SubtractiveBlending, MultiplyBlending, CustomBlending,
 	ZeroFactor, OneFactor, SrcColorFactor, OneMinusSrcColorFactor, SrcAlphaFactor, OneMinusSrcAlphaFactor, DstColorFactor,
@@ -672,6 +672,8 @@ class WebGPUPipelineUtils {
 		const descriptor = {};
 		const utils = this.backend.utils;
 
+		//
+
 		descriptor.topology = utils.getPrimitiveTopology( object, material );
 
 		if ( geometry.index !== null && object.isLine === true && object.isLineSegments !== true ) {
@@ -680,28 +682,17 @@ class WebGPUPipelineUtils {
 
 		}
 
-		switch ( material.side ) {
+		//
 
-			case FrontSide:
-				descriptor.frontFace = GPUFrontFace.CCW;
-				descriptor.cullMode = GPUCullMode.Back;
-				break;
+		let flipSided = ( material.side === BackSide );
 
-			case BackSide:
-				descriptor.frontFace = GPUFrontFace.CCW;
-				descriptor.cullMode = GPUCullMode.Front;
-				break;
+		if ( object.isMesh && object.matrixWorld.determinant() < 0 ) flipSided = ! flipSided;
 
-			case DoubleSide:
-				descriptor.frontFace = GPUFrontFace.CCW;
-				descriptor.cullMode = GPUCullMode.None;
-				break;
+		descriptor.frontFace = ( flipSided === true ) ? GPUFrontFace.CW : GPUFrontFace.CCW;
 
-			default:
-				console.error( 'THREE.WebGPUPipelineUtils: Unknown material.side value.', material.side );
-				break;
+		//
 
-		}
+		descriptor.cullMode = ( material.side === DoubleSide ) ? GPUCullMode.None : GPUCullMode.Back;
 
 		return descriptor;