3D Model Illusion Using Image Planes

Hey everyone! I wanted to know if anyone knows the name of the process where you create multiple transparent renders of objects in a scene, transfer each image to their own individual image plane, and place each plane in the position of the original objects to replace them and create the illusion of the 3D model actually being there. I’ve seen this method of polygon optimization in multiple games, but have never seen any mention of it until now. It’s sort of hard to explain so here’s a video where a guy does it (skip to 9:56 and watch til 10:15): https://www.youtube.com/watch?v=KyXRBu7gn2o

If you could also provide any in-depth tutorials or articles for this process, that’d be extremely helpful!

In games, it’s called “billboarding” or “imposters”. It’s called billboarding because usually they have the plane face the player’s camera at all times, kind of like one of those big rotating billboards.
Here’s a basic overview:

Here’s a process of making some grass assets for a game engine:

You can read about a more advanced implementation for tree LOD here:

And some even more advanced implementations have emerged for this purpose, such as this: