Let's say I have two 3D opengl scenes, each rendering to its own gl.render. (Let's call them GL3DA and GL3DB) I want to take each of those scenes, and have them shown on two separate videoplanes, themselves located within another 3D scene, let's call it GLBillboard.
So the GLBillboard scene would show the two videoplanes, as if they were objects within the scene (billboards). Each videoplane would be showing a different 3D scene.
How do I do this? I am aware that I need to do something called a "readback", that turns the output of a gl.render queue into a texture, and then apply this texture to the videoplane.
However, I can't find a lot of detail on how this is done.
Can anyone help me with this?