[jerf]

I think I wasn't clear. I mean, send 5 textured polygons to the 3D hardware, with various darkenings and offsets on one texture (which if nothing else can be done via lighting, but there's probably other easier ways), and let it do the blending en masse. Instead of using shaders and blinding it to what you're doing, it may be able to render the polygons much faster, on an optimized path. And it may not. But it's worth a try.