tranCendenZ
2[H]4U
- Joined
- Jun 6, 2004
- Messages
- 3,844
da sponge said:While I agree with your last point, I don't with the first sentence. The reason precision isn't needed at times is because some of the shaders don't appear complex enough that the extra precision provided at full precision doesn't make any difference in the output generated. The point here is that Valve should have coded it so that the card had the option to run these shaders at partial precision to improve performance if image quality wasn't effected. The shaders that DO require full precision (as seen in the comparison screenshots of the glass) would simply not have this option, forcing all cards to run at full precision. Valve bypassed this completely by forcing the most of the FX cards into dx8.1 mode when they seemingly could have provided the majority of those users with dx9 benefits without a huge difference from dx8.1 performance by adding partial precision hints where appropriate.
Yep you got it dead on.
That's of course assuming we're not missing some big reason why not to use partial precision on the majority of the shaders. Many people are jumping to conclusions as to why Valve didn't do this and assume that partial precision would have been fine for the majority of the computations in the source engine. If there's some other factor that makes partial precision a moot point, then everyone getting riled up will seem pretty ridiculous, but if it is a viable, signification perfomance boost, Valve has some serious explaining to do.
Well using 3danalyze we can see most of the shaders work fine in FP16, with a few exceptions that need FP32. Mixed mode should have been made available, as its the best performance with no IQ loss you can program. Every other dev can do it and has done it in intensive dx9 games, Valve can do it, they just chose not to. I think ATI's dollars played into this.