More Features…
3 Flavours of Bumps
Environmental Bump Mapping
I will admit that I'm left scratching my head over this feature - is it any use? Yes, undoubtedly it makes a noticeable difference in games that use it. However, are we likely to see patches for the back catalogue of game that utilise the feature for Matrox cards only? I'm doubtful! And with features such as Dot3 and Cubic Environment mapping becoming more widespread its possible that developers of future titles may be more enticed by these, and overlook EMBM. Also DX8 introduces a more general texturing operation known as dependent texture reads, this is a superset of EMBM rendering and allows for much more than just bump mapping.
Dot3
Of the two DirectX games that feature support for Dot3, Evolva and Giants: Citizen Kabuto, neither appears to work with KYRO. Evidently Giants has taken the option of looking for a T&L unit and enabling Dot3 if present, because both GeForce and Radeon have a T&L unit and Dot3 support; of course, this precludes cards without T&L (as its not required for Dot3) and hence KYRO. Evolva appears to be a slightly different case; with the patch bump mapping can be enabled, however when you compare the results to GeForce you can clearly see that something is amiss…
Evidently this is an issue with how KYRO handles the specular iterator that Computer Artworks use for the Dot3 Bumpmapping effects in Evolva; it is compatible with GeForce and Radeon, but not KYRO. However, a patch has been written, which uses the diffuse iterator which all three Dot3 cards handle in a similar fashion, we are just waiting for Computer Artworks/Interplay to make it available…
It thus seems that while KYRO supports DX7 Dot3 functionality most developers are not using it fully correctly (caps checking) or are using a flexibility that KYRO does not support (the DX specs are never 100% clear on what is allowed and not allowed). Fact is the DX7 and 8 bumpmap demos run fine on KYRO but that doesn't mean that games will. Who is to blame?
In any case, Dot3 is a nice addition to the chipset, but one that's got to be pushed to the developers. Again, we will soon have cards with full DirectX8 Pixel Shader functionality; I hope that Dot3 isn't a feature that will be overlooked by developers in favour of newer more advanced ones.
For an in-depth explanation of Bumpmapping see Kristofs articles here, and the PowerVR EMBM white paper.