[SDL] grabframe

NighTiger nightiger at gameprog.it
Sat Jan 22 16:25:30 PST 2005

On Thu, 06 Jan 2005 15:52:39 -0300, Gabriel <mystml at adinet.com.uy> wrote:
> What you can do though, if you don't need a lot of depth buffer
> precission, is to use the range 0 - 0.5 in one frame, and then 0.5 - 1
> in the next, then 0-0.5 and so on, thus removing the neccessity to
> clear. I don't remember the specifics but there was a way to do that.

I saw something like this just today, which involved switching the
clearing mode itself from GL_LESS to GL_GREATER with each frame as
well.  As I fail to grok why this would work for the moment, I'm going
to try option 3 first.

> > Third thought is to throw in a skybox of some kind, which will in
> > theory remove the need to clear the color buffer with each frame.
> This one is correct, and in fact, widely used. If you played Doom or
> Duke Nukem 3D, and used one of the clip hacks, stepping out of the map
> caused the background to become dirty. That's because the games assumed
> the map was closed, and therefore didn't clear the color buffer at all.

I distinctly recall liberally using IDCLIP, heh.  Excellent, this will
be where I start then - thanks much!  I'm very curious to know,
though, why mapping a texture across the entire screen would be so
much faster than setting a single color value across it all.  Any
insights to offer?


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