alpha testing a blended texture

I would like to blend two alpha textures and then perform alpha testing on the resulting blended texture. What is the best way to do this? When I enable alpha testing and do the blending, then the alpha testing is performed before blending. I also tried using the accumlation buffer (because I’m blending the alpha textures at atypical proportions like 25% of one texture and 75% of the other). But again, when I enable alpha testing after the calls to accumulate, but before writing back the result, it seems to perform the testing before the textures get put into the accumulation buffer. Would alpha blending or multi-textures be a better way to go? Basically, I’d like to do alpha testing on the results from blending 2 textures. Thanks for any help you all can give! - Q.

If you’re multipassing, you’ll have to render both passes to a texture which you then render to the framebuffer with your alpha test.

If you’re multitexturing, however, you just do the blend, but keep the alpha value around. Then, you just let the alpha test work. Remember, the alpha test isn’t on a texture; it’s on the outgoing fragment.