CSAA

I was kind of planning on working through NeHe's tutorials but after blazing through the first 10 I realized I hadn't really forgotten that much and actually had a pretty good idea of what I was doing. Still, it was a nostalgic trip.

I decided that I really needed anti-aliasing. And not just some generic MSAA, I needed CSAA ("Coverage Sample Anti-Aliasing") an extension available on NVidia's GeForce 8 cards. NVidia has a page with details (also GL_NV_framebuffer_multisample_coverage), but basically they claim that it "rivals the quality of 8x or 16x MSAA" while having overhead comparable to 4x MSAA. The screenshots at the bottom of their write-up seem realistic basic on my test application so I won't bother (re-)posting them here, but it looks pretty nice.

They also mention that by "decoupling coverage from color/z/stencil" it's extremely efficient in terms of bandwidth and storage costs. They provide some information about the number of samples taken (at 8x CSAA; 4 color/z/stencil and 8 coverage samples), but there isn't a lot of details about storage requirements. I think I've figured out how to measure GPU computational overhead with reasonable accuracy (GL_EXT_timer_query) so I can partially check on their claims of how it compares to 4x MSAA, but I'd like some way to get a better idea about CPU<->GPU bandwidth and VRAM usage. NVidia's PerfHUD may be the answer to my prayers. I'll take a look as soon as I get the chance.

The storage requirements in particular worry me because the storage cost of 4x or even 2x multi-sampling at resolutions around HD is already quite high (despite not looking all that great), and you run the risk of having to move things to main memory and performance suffering.

Back to OpenGL...

Being moved to PS3 stuff at work has really revitalized my interest in OpenGL and programming in general. I figured it was high time to bring myself up to date regarding OpenGL after so many brief flings with DirectX since it was now more relevant (for me, at least). All of this prompted me to brush off this blog since I seem to be able to concentrate my efforts on something a lot better if I write about it.

I had never used OpenGL extensions before, but I found some good info about them at opengl.org. I lifted the isExtensionSupported() function to help me check for capabilities supported by the graphics driver/card and made a short macro to help me get function pointers with wglGetProcAddress(). It seems clunky but with a bit of wrapping and macro/template magic I should be able to get something decent going. I found out about GLEW from NVidia's OpenGL SDK, but I've decided to handle extensions myself for the moment since it will force me to look into them a bit more closely and I figure I won't be using that many anyway. We'll see how my patience holds up.