I saw a video of an 2.5d engine that used heightmaps to do zbuffering. Is this hard to do? I have more or less no idea of Opengl(lwjgl) and that stuff.

I could imagine, that you compare each pixel and its depthmap to the depthmap of the already drawn background to determine if it gets drawn or not.

Are there any tutorials on how to do this, is this a common problem? It would already be awesome if somebody knows the names of the Opengl commands so that i can go through some general tutorials on that. greets!

Great 2.5d engine with the needed effect, pls go to the last 30 seconds

Edit, just realised, that my question wasn't quite clear expressed: How can i tell Opengl to compare the existing depthbuffer with an grayscale texure, to determine if a pixel should get drawn or not?