Dirty water, bubbles, and soap suds in Maya

IMPORTANT NOTE: I think I forgot to mention the most important thing for the foam. In the shape node of the geometry (of the foam object) you have to go to Arnold - Volume Attributes - and set "step size" and "volume padding" to a small non-zero number (try 0.1 for each). I may have mentioned it but I recorded this one a couple of times... Render dirty water, bubbles, and sudsy soap with Arnold in Maya. This uses some presets of the aiStandardSurface shader a the aiStandardVolume for the suds. It's not quite physically accurate, but it looks good enough!