   Using gatheralpha for alpha test - problem with BC3 (DXT5) textures
Hi - I've implemented a pretty effective alpha test using Texture2D.GatherAlpha, works even better with alpha-to-coverage enabled.  If it gets past the clip(), i multiply the scalar alpha return value with the final color.cbuffer PAlphaTest : register (cb2){  float4 alphaTestThresh;};float MainSampleAlphaTest (Texture2D tex, SamplerState samp, float2 texCoord){  float4 alphaSamp = tex.GatherAlpha (samp, texCoord, int2(0,0));  float alpha = dot (alphaSamp, 0.25);  clip (alpha - alphaTestThresh.x);  return (alpha);}WIth a DXGI_FORMAT_R8G8B8A8_UNORM_SRGB texture I get this: [attachment=28982:a0.jpg] WIth a DXGI_FORMAT_BC3_UNORM_SRGB texture I get this: [attachment=28983:a1.jpg] Strange bunch of lines with the BC3 texture - anyone seen this effect before?Thanks. 
I've seen driver bugs in the past when gather is involved. Did you test that you actually get the proper results if you issue four regular samples?;On the plus side, your bugged screenshot looks like a nice world map :D;I've seen driver bugs in the past when gather is involved. Did you test that you actually get the proper results if you issue four regular samples?I agree, it sounds like a driver bug. You can also try using the reference device to see if that produces the correct results. If it does, then it's probably a driver bug.   ;Thanks for all your replies.  The good news is, not a driver bug - this was my bug, a cross-up in identifying the texture format.  The DXT5 was being loaded as BC2 intead of BC3.;Out of interest, what advantages did you feel your use of Gather gave over bilinear filtering, if any?