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Thread View: comp.graphics.api.opengl
2 messages
2 total messages Started by Daniel Ludwig Wed, 12 May 1999 00:00
"Do It Yourself" lighting with OpenGL
#56
Author: Daniel Ludwig
Date: Wed, 12 May 1999 00:00
22 lines
1238 bytes
Hi,

I'm currently using OpenGL for rasterization only, doing my
own transformations, lighting & clipping calculations. Now
to my question: is it possible to set up OpenGL to compute
the resulting frame buffer color using this formula:

color = texture RGB * iterated RGB + iterated Alpha
(using iterated Alpha as monochrome specular component)

I've done this already with Glide, and AFAIK it's also possible
with Direct3D, but is it possible _without_ using OpenGL's
internal lighting pipeline?

I think I could "emulate" this equation using alpha blending
and multi-pass rendering, but this would cost performance.




Thanks,
Daniel
Re: "Do It Yourself" lighting with OpenGL
#55
Author: Angus Dorbie
Date: Wed, 12 May 1999 00:00
39 lines
1964 bytes
There's the post texture specular highlight in OpenGL 1.2 which may be
there as an extension before 1.2.

This holds off on the addition of all lighting specular terms until
after the texture environment.

Cheers,Angus.

Daniel Ludwig wrote:
> 
> Hi,
> 
> I'm currently using OpenGL for rasterization only, doing my
> own transformations, lighting & clipping calculations. Now
> to my question: is it possible to set up OpenGL to compute
> the resulting frame buffer color using this formula:
> 
> color = texture RGB * iterated RGB + iterated Alpha
> (using iterated Alpha as monochrome specular component)
> 
> I've done this already with Glide, and AFAIK it's also possible
> with Direct3D, but is it possible _without_ using OpenGL's
> internal lighting pipeline?
> 
> I think I could "emulate" this equation using alpha blending
> and multi-pass rendering, but this would cost performance.
> 
> Thanks,
> Daniel

-- 
"Microsoft's system was like a forest that hadn't had a controlled
 burn in decades, just waiting for one person with a match to turn
 it into a disaster. Melissa was Microsoft's fault. They left their
 system wide open to this sort of abuse, they knew it could happen
 and did nothing." -- Bruce Perens

For advanced 3D graphics Performer + OpenGL based examples and tutors:
http://www.dorbie.com/
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