Subject: Re: (type-of 1.0f0)
From: (Rob Warnock)
Date: Thu, 06 Feb 2003 03:21:15 -0600
Newsgroups: comp.lang.lisp
Message-ID: <>
Kenny Tilton  <> wrote:
| But OpenGL still is not working from LW for me, and all I am trying to 
| do is clear the screen to different glClearColors. Not a lot to ask. I 
| actually get noise, sometimes recognizable as if some other window's 
| device context is being sucked in (or just a win32 display buffer 
| somewhere).

You probably already know all of the following, and if so,
"never mind", but...

You might try doing a "swapbuffers()" [or whatever they call it
in OpenGL these days]. IIRC from my days at SGI (though I was a
networking person, not graphics), the basic IrisGL and OpenGL
rendering models were to render into the "background" frame buffer,
then when you're done with drawing that frame, do a "swapbuffers()"
(or eq.) which -- after delaying until the next vertical retrace! --
flips some address bits in the graphics engine (or card) so that the
foreground & background frame buffers swap roles. [Nota bene: no data
is copied during this operation! Only the identities of "front" and
"back" are swapped.]

Then you start rendering the next frame into the "new" background
buffer, starting with "clear()" and drawing the entire picture again,
then issue a "swapbuffers()", etc. Think of a FORCE-OUTPUT that you
can only call 60 times a second at most. [Well, you can *try* to call
it faster, but it won't return from a call until the next VIR...]


Rob Warnock, PP-ASEL-IA		<>
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