There's a more general thread on the ATI Radeon X1x00 series
here... but I was just reading the coverage over at
Beyond3D and I spotted this little fragment:
Quote:From this page:
However, one element of Vertex Shader 3.0 compliance is the capability for vertex texturing, yet there appears to be an absence of any texture lookup capabilities from ATI's diagrams
I'm gonna go double check my docs, but from that article it indicates that vertex texturing via D3D9 only works with a set of texture formats as exposed by the driver. The ATI hardware exposes
no texture formats as compatible.
It seems that there is a loophole in the SM3 specification that allows the hardware to be "SM3 compliant" yet effectively disable vertex texturing.
Clever loophole I suppose.
Quote:as somewhat of an alternative to Vertex Texturing ATI will be promoting the use of a new extension to DirectX know as Render to Vertex Buffer...
--- Snip ---
...rather than rendering to a displayable surface or texture the results are rendered to a buffer in memory that can be directly read as an input to the vertex shader. The upshot of this process is that an application can have access to the capabilities of the Pixel Shader which can then be fed back into the geometry processing pipeline, which should result in a superset of capabilities of vertex texturing and should actually perform better than current vertex texturing schemes because the pixel pipelines are inherently built to better cope with the latencies of texturing.
Sounds clever from a hardware point of view, but a little clunky from a graphics engine / software development point of view.
Anyone here played with vertex texturing on the GeForce 6x00/7x00? Do they have the same limitation? Can they do this "R2VB" stuff that's mentioned by ATI?
A little tech demo I was thinking about would require vertex texturing support [headshake]...
Cheers,
Jack
