[GLQuake] Depth Buffer Precision and Clearing Fix

[mh]

[Sajt]

[Baker]

I ran the Win32 GL build of my engine with 16, 24, 32 z buffers requested (no stencil buffer requested) using -bpp 16.

[My engine defaults to the desktop bpp unless otherwise specified so I actually have to do -bpp 16 to get 16 bit color ... to enable switching between fullscreen and windowed mode without reuploading 2D textures as I do not yet have a texture manager capable of re-uploading all the 2D pixs.]

timedemo demo1 results:

32 bit z buffer requested: 295 fps
24 bit z buffer requested: 204 fps
16 bit z buffer requested: 295 fps

I don't know how to interpret the results except at least by starting the engine and doing a timedemo of demo1, I'm not seeing a frames-per-second performance drop off by not clearing the stencil buffer?

[mh]

[Spike]

[leileilol]

[mh]

Curioser and curioser. I always get 16-bit depth unless I explicitly request 24, and then I always get 8-bit stencil too, even if I request 0. D3D is a lot clearer than OpenGL here (you get exactly what you ask for and no messing) but with the downside that you need to check that what you ask for is actually supported first, otherwise it'll blow up. Pros and cons to both approaches.

[Spike]

You could walk the list of them with DescribePixelFormat until it fails, in order to enumerate the provided modes and pick the one that best matches your needs.
Which is basically what ChoosePixelFormat does anyway.

[mh]

[Baker]