postprocessing with reflector performance problem quick hack.

https://discourse.threejs.org/t/hows-the-reflection-made-in-this-example/23597/8

Author: gonnavis

examples/jsm/objects/ReflectorForSSRPass.js

@@ -91,6 +91,9 @@ var Reflector = function ( geometry, options ) {
 	this.material = material;
 
 	this.onBeforeRender = function ( renderer, scene, camera ) {
+		if (!window.needReflector) return;
+		window.needReflector=false
+		// console.log('onBeforeRender')
 
 		reflectorWorldPosition.setFromMatrixPosition( scope.matrixWorld );
 		cameraWorldPosition.setFromMatrixPosition( camera.matrixWorld );

examples/jsm/postprocessing/SSRPass.js

@@ -348,7 +348,8 @@ SSRPass.prototype = Object.assign(Object.create(Pass.prototype), {
 
     if (this.encoding) this.beautyRenderTarget.texture.encoding = this.encoding
     renderer.setRenderTarget(this.beautyRenderTarget);
-    renderer.clear();
+		renderer.clear();
+		window.needReflector=true
     renderer.render(this.scene, this.camera);
 
     // render normals