This detailed feedback really helps me a lot. I think most of the thing you've pointed out can be fixed, and as soon as I can, I'm going to take a look at them. And I've suspected of these two scenes when you said that framerate sometimes drops, because they are the ones with >= 6 portals that really need to be rendered :(. That means that the renderer has to do all the render process (even z-buffering) >= 6 times every frame because each portal has a != camera. As I said, I want to turn this project into a unity package, so optimization and code review are on top of my list (I'm learning some new techniques that might help). Thanks for the help!