Thanks for your reply, @TesterY. I really appreciate it. The filter is now working correctly. The important thing is not to change the background color (default = black) of the `ViewPort`. That was the cause of the problem I was having. Another optimization you can add to the filter is to avoid continuously creating a new `SceneGraphVisitor` in the `postQueue()` method, but rather to create a single class variable that can be reused each time. @Override protected void postQueue(RenderQueue queue) { Renderer renderer = renderManager.getRenderer(); // 1. Render objects to the mask FrameBuffer renderer.setFrameBuffer(maskFrameBuffer); renderer.clearBuffers(true, true, true); // Render each selected spatial using the mask material for (Spatial sp : selectedSpatials) { sp.depthFirstTraversal(maskVisitor); } // 2. Pass the generated mask texture to the final filter material this.material.setTexture("MaskTexture", this.getMaskTexture()); // 3. Reset the FrameBuffer to the main viewport output renderer.setFrameBuffer(viewPort.getOutputFrameBuffer()); } private final SceneGraphVisitorAdapter maskVisitor = new SceneGraphVisitorAdapter() { @Override public void visit(Geometry geo) { renderManager.setForcedMaterial(maskMaterial); renderManager.renderGeometry(geo); renderManager.setForcedMaterial(null); } };