I'd like to submit vertex data that is already in screen space. I realize that I can jigger the transformation matrices and viewport parameters to get this to work, but I'm wondering if there is any way to hint to the driver that these can be sent directly to the rasterizer without going through any part of the transformation pipeline. I'm also concerned that these vertices will have to be back-transformed from screen space into projective clip space in order to be clip tested. I don't need them to be clipped, but I'm having trouble trying to find out how to disable frustum clipping.
So I guess my question boils down to, "What's the most efficient way to draw 2D primitives using OpenGL ES?"
Thanks for your help!