How does the scattering node's density actually affect density, and what units is it in?
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An issue I've come up against repeatedly, in my search for physical realism beyond basic hard surface models, is that there are no units attached to any part of the scattering node. The lack of any meaningful measurement is a bit unfortunate, compared to the seemingly similar SSS shader. In SSS it's very clearly stated that it measures dropoff in mm, with the radius being distance between scattering events (like average distance between bubbles in a colloid), so it's relatively easy to measure the effects alone, but without any kind of measurements in the volume scattering in the documentation or otherwise, I've had to resort to my own testing and finally, asking you guys about it.
so, because volume scattering, (as far as I know) is based off of SSS and regardless must make some kind of measurement in the scene for its calculations, what is its unit? from particles interacted with per step, to particles per mm, or mass of particulates in a certain space, even percentage of light scattered per x units is fine, but we need some kind of hard measurement listed in the documentation or program to signify it.