   R2VB - vertex texture fetch
  I need to implement a height-field (it's a 3d graph type thing) and was wondering if anyone has any experience of the R2VB extension.  Is it available in DirectX?  If so, what's the performance like?  I have to base my code on D3D9, so I can't use 10.1 or displacement mapping in 11.This thing will need to run on fairly old systems too (up to 5 years old), with up to date drivers of course.  So, is R2VB a possibility, or shall I continue with my design which involves the CPU displacing the patch and then sending it up to the GPU?Thanks for any insights you might have.   
  R2VB is implemented as a D3D9 "extension" (AKA driver hack) for ATI GPU's, 9500 and up. You'll want to read this for all of the details.The performance is definitely good enough that it's practical to use when it's available, but the main problem is that it only works on ATI hardware. For Nvidia DX9 GPU's you don't really have a good equivalent...you can use vertex texture fetch for 6 and 7-series, but it's pretty slow. For any DX10-level GPU vertex texture fetch is much quicker, so you could use it without a problem.   ;  Ok, thanks for your reply.  I think I'm just not going to bother doing it.  I can see great pain and suffering in the future if I try to do it with such a varied hardware base.   