Thread View: comp.graphics.api.opengl
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Started by Daniel Ludwig
Wed, 12 May 1999 00:00
"Do It Yourself" lighting with OpenGL
Author: Daniel Ludwig
Date: Wed, 12 May 1999 00:00
Date: Wed, 12 May 1999 00:00
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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
Author: Angus Dorbie
Date: Wed, 12 May 1999 00:00
Date: Wed, 12 May 1999 00:00
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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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