In my application all of the 3D stuff is in perspective mode and all of the User Interface is in orthographic mode. Right now there is a 50% transparent strip across the bottom for the interface. When I try putting an icon on top of the strip, the icons 100% transparency shows through the strip (cancelling out the 50% transparency in the strip). I''m using TGA for the icon and strip. Right now the icon is displayed first, then the strip so that the icon is on top of the strip. What blend function do I need to use and when do I need to use it?

Fixed my own problem. I use glAlphaFunc() to cancel out all pixels with alpha over 0.5.