I have a continuous height-mapped mesh to represent landscape. I use the stencil test to create holes in the mesh. I draw holes to the stencil buffer and then use it to discard mesh fragments. Everything works fine except that my holes are visible through the mesh even if they are occluded by higher ground.
Is there any way to apply depth testing to a hole, keeping my mesh drawn in a single call to glDrawElements?
The easiest way to do this is to render the holes as geometry first (a simple quad is ok), with color writes off and depth writes on. This allows terrain in front of the hole to draw over it and terrain behind the hole will fail the depth test. That leaves a [clear color] hole in the terrain that you can render through.
This is often done to clip the water plane out of the interior of a boat's hull.
I would advise you to consider using glStencilOp function.
In particular, you can use different operation if the stencil test passes but not the depth test.
See that reference page for additional details.
Hope it helps.
