Needed to use an rgba format to use floats (and optimal layout), but
having to set the alpha to 1 even for full-dark luxels is not very
efficient. Better to just ignore the alpha in the shader. Fixes the
occasional transparent surface in shadowed areas.
Many surfaces are missing (I suspect it's due to transform stage
management in the index emitter), and currently only the light maps are
rendered (still not binding the correct textures), but the basics are
working.
There's still a problem with the vertex data itself not getting sent to
the GPU properly, but vulkan is now happy with my tiny test map (which
required disabling skies entirely until I get null textures working).
