Error with Fetch4 directional shadows on Radeon 5750

Discussion created by limeygrendel on Dec 18, 2009
Latest reply on Apr 27, 2010 by frali
Edges of shadows are not smooth like other Radeon GPUs with Fetch4 support.

We have run into a visual error with my directional shadow maps when running on a Radeon 5750.  It's hard to explain, but the edges of the shadows appear very blocky.  In order to verify that it wasn't our implementation, I checked the Radeon SDK ShadowMapFetch4 ( and it displayed the same visual error. 

If I had to guess, I'd say it isn't actually fetching 4 depth values, but instead is returning a single depth value in r, g, b, and a.

We've tested it on 2 different systems with the 5750 and both showed the error.  One system was a Windows Vista 32-bit and the other was Windows 7 64-bit.

We've test it on various other Radeon GPUs (x1950, 4650, 4850) and haven't seen any problems.

Could this be a driver issue or possibly something more sinister?