opengl z-sorting transparency

Question

im rendering png\'s on simple squares in opengl es 2.0, but when i try and draw something behind an square i have already drawn the transparent area in my top square are ren

Answer 1

Your title is essentially the answer to your question!

Generally transparency is done by first rendering all opaque objects in the scene (letting the z-buffer figure out what's visible), then rendering all transparent objects from back to front.