I'm trying to figure out a way to render content in my scene such that it gets rendered *additively*. I've been experimenting with glBlendFunc() and glTexEnvi(), but I always seem to end up with an ordinary transparency effect with the resulting pixel value somewhere between the source and destination.
Can someone post a snippet of code with working pixel addition, i.e. where the resulting pixel is *brighter* than either the source or destination? I'm sure it's not as difficult as I'm making it, but I can't quite get it right.