That is actually quite interesting. I will definitely try that. I feel there might be issues with a volume, containing cavities or discontinuities, but for something relatively uniform, like a cloud, probably it could work. My sincere gratitude for suggestion.
I’ve already tried 4 bit values. There was very noticeable stepping in shadowing, sadly.
I just thought about another approach, where each frame in the texture would be further split in two parts, and I would choose which part to sample depending on either it is positive or negative per-axis direction towards light. I haven’t tried it yet. Feels scary. Besides I would loose quite a bit of resolution for light transmittance. Might be worth trying that too.