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3Dc Nvidia

OpenGL

Started by n00body Mar 19, 2007 at 7:08 PM 5 replies 1.9k views

Original Post

n00body

Mar 19, 2007 at 7:08 PM

Is there a way to utilize 3Dc normal maps on an Nvidia GPU (6800GT, fyi) under OpenGL? If so, does it have any limitations in comparison to doing it on an ATI GPU?

V-man

163

V-man

Mar 20, 2007 at 2:57 AM

If GL_ATI_texture_compression_3dc is supported, yes.
Here's a demo http://www.ozone3d.net/tutorials/bump_map_compression_p5.php#o3tc

n00body

Author

n00body

Mar 20, 2007 at 7:24 AM

If I had that extension, I wouldn't be asking. I had heard that they worked out a way to decode 3Dc maps using the s3tc extension, so that their older cards could take advantage of the new technology. I thought that this could be applied to use on an Nvidia GPU as well. Any comments?

_the_phantom_

496

_the_phantom_

Mar 20, 2007 at 7:47 AM

iirc you can just upload a 3Dc normal map as a two component texture and perform the decode in a fragment shader on hardware which doesn't support the extension directly.

On pre-shader hardware however I don't know how you'd do it.

n00body

Author

n00body

Mar 20, 2007 at 12:19 PM

But does doing it that way cause a severe performance hit, as compared to the GPUs that support it in hardware?

_the_phantom_

496

_the_phantom_

Mar 20, 2007 at 1:13 PM

I believe it will cost you 2 or 3 instructions, which if you are bandwidth limited and not ALU limited shouldn't cause you a problem

n00body

Author

n00body

Mar 24, 2007 at 10:56 PM

So I have to finish decompressing it with a fragment program function. However, assuming that I already have the .dds parsed, how do I actually get the data into OpenGL? Do I just load it like I would any other DXT data?

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