Example gpgpu_water: Fix tennis balls

examples/webgl_gpgpu_water.html

@@ -646,8 +646,11 @@
 						var v = 1 - ( 0.5 * sphere.position.z / BOUNDS_HALF + 0.5 );
 						readWaterLevelShader.uniforms[ "point1" ].value.set( u, v );
 						gpuCompute.doRenderTarget( readWaterLevelShader, readWaterLevelRenderTarget );
+						var previousRenderTarget = renderer.getRenderTarget();
+						renderer.setRenderTarget( readWaterLevelRenderTarget );
 						gl.readPixels( 0, 0, 4, 1, gl.RGBA, gl.UNSIGNED_BYTE, readWaterLevelImage );
 						var pixels = new Float32Array( readWaterLevelImage.buffer );
+						renderer.setRenderTarget( previousRenderTarget );
 
 						// Get orientation
 						waterNormal.set( pixels[ 1 ], 0, - pixels[ 2 ] );
@@ -798,4 +801,4 @@
 
 		</script>
 	</body>
-</html>
+</html>