MATERIAL BREAKAGE: this change breaks materials
In order to use one less sampler, we now use a UBO instead of a texture
to store the "froxel records". Currently this UBO is limited to 16KiB
vs. 64KiB before with the texture.
We also handle running out of record space better, by using a predefined
record that has all the lights in the scene. This way the scene will be
rendered properly, albeit at a potentially large performance cost.
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