Posted by Joseph J. Strout on January 21, 2004 at 11:54:54:
At 2:14 PM -0500 1/21/04, Frank C. wrote:>This is a problem with how Quesa handles texture transparency...
>
>To work like QD3D, Quesa resorts to using additive blending for
>textures with alpha channels (that's why you have to pre-multiply
>alphas to get a modulated blend instead of additive). A side effect
>of this is that vertex attributes like fog and specular highlights
>will be blended additively as well, resulting in the effect in your
>screenshot.Aha! I've been seeing this, too. It's more noticeable on some video
cards than others, but when there's a decent amount of fog, it looks
pretty cruddy on all of them. But I had not yet taken the time to
dig into the cause.>There's no real way of fixing this without adding some face/vertex
>attribute extensions that allow you to explicitly assign blend modes.Extensions to what? You're not proposing that we need new Quesa APIs
for dealing with this, are you?I'll cheerfully expose my OpenGL ignorance here; can you explain in
more detail why it's difficult to use additive blending for textures
but not for fog?Thanks,
- Joe--
,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| joe@strout.net http://www.macwebdir.com/ |
`------------------------------------------------------------------'