WebGPURenderer: Fix viewport regression with array cameras. (#34424)

Author: Mugen87

src/renderers/webgl-fallback/WebGLBackend.js

@@ -1266,7 +1266,7 @@ class WebGLBackend extends Backend {
 
 			const renderTarget = this._currentContext.renderTarget;
 
-			const pixelRatio = renderTarget !== null ? 1 : this.renderer.getPixelRatio();
+			const pixelRatio = ( renderTarget === null || renderTarget.isPostProcessingRenderTarget === true ) ? this.renderer.getPixelRatio() : 1;
 			const isRenderCameraDepthArray = this._isRenderCameraDepthArray( this._currentContext );
 			const prevActiveCubeFace = this._currentContext.activeCubeFace;
 

src/renderers/webgpu/WebGPUBackend.js

@@ -2257,7 +2257,8 @@ class WebGPUBackend extends Backend {
 
 			}
 
-			const pixelRatio = context.renderTarget !== null ? 1 : this.renderer.getPixelRatio();
+			const renderTarget = context.renderTarget;
+			const pixelRatio = ( renderTarget === null || renderTarget.isPostProcessingRenderTarget === true ) ? this.renderer.getPixelRatio() : 1;
 			const indexPos = cameraIndex ? bindings.indexOf( cameraIndex ) : - 1;
 
 			for ( let i = 0, len = cameras.length; i < len; i ++ ) {