6 Replies Latest reply on Jun 30, 2010 4:54 PM by Colin Brougham

    Alpha channel weirdness with hardware MPE

    Colin Brougham Level 6

      To begin, I'm using a GTX 480 with the hack, so I'm not going to complain too loudly it this is a result of using as-yet unsupported hardware. However, I just want to verify with other hardware MPE users (both legit and unsupported) if this issue is happening on other systems.

       

      I've noticed some oddities with imported PSD files and the way that their alpha channels are rendered with hardware MPE, versus software MPE. I'm putting up a couple frame grabs with GPU acceleration turned on and off at couple different point where I'm using the PSDs. Forgive the PNG compression; you should be able to see the difference, nevertheless.

       

      First up, 100% opaque text over a background. The edges of the text are... fuzzy, maybe?

       

      Software:

      SW_MPE_01.png

      Hardware:

      HW_MPE_01.png

       

      Second, a couple layers Fast Blurring and fading in. The logo is 100% opaque, and there is a separate "glow" layer (rasterized in PS) behind it. Pretty obvious, here...

       

      Software:

      SW_MPE_02.png

      Hardware:

      HW_MPE_02.png

       

      Finally, a mostly-transparent logo bug. The hardware version is not as transparent.

       

      Software:

      SW_MPE_03.png

      Hardware:

      HW_MPE_03.png

       

      The only difference between each of these examples is that I turned on or off GPU acceleration in the Project Settings; it's the same PSD for each grab. I've also noticed that standard cross dissolves are a little chunky when dissolving to or from a graphic (even a flattened version); the opacity change is not as linear as it usually is. In software mode, this goes away.

       

      Anyone witnessed similar results? Again, I want to believe that this is just a result of using the GTX 480 and the hack, without official support. It could very well be the nVidia driver, too, I suppose, but I haven't tried rolling back to check that (I'm running the latest versions).

       

      Thoughts?