ATI has work around VTF lack

SHORTLY after we posted our original filing here ATI's Developer relations manager Richard "7 of 5" Huddy responded with what is really happening with ATI's Vertex texture fetch. What we like about ATI Europe is it can speak for itself while Nvidia is more Borg like marchitecture as the US has to confirm everything ultimately.

Anyway Richard Huddy confirmed that the X1000 generation of R520 based cards and derived R530 and RV515 ca not directly support vertex texture fetch (VTF). ATI decided to do it as an optional feature of Shader model 3.0. I guess ATI would support it if it could but it found another way around it.

ATI supports a feature called Renter to Vertex Buffer (R2VB) and it allows developers to do anything that they would want of VTF. "In its simplest form you can see that R2VB is capable of everything that VTF can do because you could trivially simply copy the vertex texture data into the vertex stream using R2VB." He added.

He believe that this is better than just doing vertex texture cache. Render to vertex buffer is built on the pixel Shader and therefore you will have all the Shader's texturing capabilities.

When Nvidia is doing Vertex texture fetch it is limited to only isotropically point samples of two different texture formats. If you use ATI's Render to Vertex Buffer you can anisotropically trilinear filter any texture format that ATI supports. ATI believes that Renter to vertex buffer is just more flexible and better way to solve the same problem and even more. [Golly, my head's reeling. Ed.]

We will ask developers what they think about this ATI versus Nvidia feature war as the technologies both can do the same thing, just the other way around. We wonder what is better to do. µ