Multiple Overlaying Scenes with Defaultrenderingpipelines

I’m working on a project with two scenes that are on top of each other. The scene in front is supposed to have a transparent background with the other scene being visible in the background. This all works well… until I try to add a DefaultRenderingPipeline to the foreground scene. As soon as I do that the scene turns opaque and I can’t see the scene in the background. Here is a simple playground example based on the official multiscene example (which is supposed to look like this). What can I do to fix this? Already tried various things, like setting the clear color to something transparent, but nothing seems to work.

ping @Evgeni_Popov

Welcome aboard!

When using the default rendering pipeline (or any post process), the rendering is done in a separate framebuffer and is copied back to the canvas at the end. In your case you need a blending instead of a copy to avoid loosing the first scene. Also, for the blending to work, you should have alpha = 0 for the background pixels of the foreground scene.

So, you need to enable alpha blending on the last post process and use a clear color like (0,0,0,0) on the first post process:

There’s a small oddity in that if you have a single post process in the chain, setting an alpha mode on this post process will disable its clearing, so you need to do it yourself (see lines 112-116).


Perfect, that works. Thank you!