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BattleMaster

Pixel shaders and Doom

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Hi

I was wondering. Will Doom III take advantage of pixel shaders to produce all that wonderful lighting?
If so, will there be a difference in image quality from fx. a GF2 to a GF3 or will it primarily be a performance issue?

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BattleMaster said:

Well, sorry. I didn't know.
Can I do this myself and if so, how?
I tried deleting my previous thread, but was not allowed to do so.

You just wait for the moderator to move it for you - simple. No, you can't do this yourself (not that I know of). Oh and sorry that I get pissed in your other thread, but I do get a bit tired of moving threads from D3 General to D3 Tech - it happens way too often.

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No problem, I understand how one would get annoyed by peoples general inability to do simple things correctly.

I'll be good from now on, I promise :D

Edit: btw, I appreciate the fact that people still exist who actually have the word "sorry" in their vocabulary. Generally people get pissed off way to easily in forums these days. So I hope we'll get along fine from now on :D

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Yeah, well, I suppose dsm takes some time getting used to :)

To answer your question, I don't know about any specific pixel shading things going on in the Doom III engine. I do believe John Carmack has said the game will look practically the same on all target video cards, at the expense of perfomance on the lower-end hardware.

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Pixel shaders will be used extensively on hardware platforms that support it-- one of the big features of the Doom3 engine is the range of custom per-card code. Pixel shaders are a huge help in doing specular highlight calculations, among other things (perhaps some tangent space calculations????). The use of pixel shaders will result in increased performance on the relevant cards, as well as increased accuracy in the lighting (for example, the specular highlights on the GF1 use sort of a hacked linear ramup, while the GF3 cards might have a more natural exponetial-looking curve).

There are some obscure cards on which the game will look signifgantly different-- cards that don't use id-supported extentions will use standard OpenGL dot3 extentions, which don't allow specular highlights. In addition, for increased performance, lower end cards can cut out specular highlight calculations and stuff.

Vertex shaders are another nice thing to have (which the GF1/2 doens't have), and which people often overlook as being un-important. However, they must be used for every light, every frame, to orient the bumpmaps properly on the model. This mean, on the GF1/2, each model has to be CPU proccessed for every light affecting it, and hand sent to the graphics card...for every light. This is bad, and vertex shaders remove the need to do this on the CPU-- it's all done in the graphics card.

Hope this helps.

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Lord FlatHead said:

Yeah, well, I suppose dsm takes some time getting used to :)

So do most of you guys...

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