SSGINode: Fix clear color. (#31881)

examples/jsm/tsl/display/SSGINode.js

@@ -354,7 +354,7 @@ class SSGINode extends TempNode {
 
 		// clear
 
-		renderer.setClearColor( 0xffffff, 1 );
+		renderer.setClearColor( 0x000000, 1 );
 
 		// gi
 

examples/webgpu_postprocessing_ssgi.html

@@ -49,6 +49,7 @@
 				camera.position.set( 2.8, 1.8, 5 );
 
 				scene = new THREE.Scene();
+				scene.background = new THREE.Color( 0xffffff );
 
 				renderer = new THREE.WebGPURenderer();
 				//renderer.setPixelRatio( window.devicePixelRatio ); // probably too costly for most hardware