I’ve written a small test program in which I use a texture with alpha values on point sprites. Things work as expected, alpha testing and blending do what I want.
Then I dropped the code into a larger project that has had many people work on it over many years. Initially, to debug, I applied the same texture to two quads and got things working, finding the appropriate state I needed to modify.
Now everything I want to do with alpha works just fine for the quads, but when I comment out glBegin(GL_QUADS) … glEnd() and uncomment the point sprite code, nothing works with alpha values.
So, since I have a something that works in a simple environment that doesn’t work in a more complex one, I figure it must be some sort of state issue … but then essentially the same technique on quads works.
What state affects GL_NV_point_sprites that doesn’t have an effect on simple texture mapping?
I hope I’ve outlined the problem clearly enough. Can anyone give me input?