I was watching this video:
https://youtu.be/gcQrzoTniU4 [youtu.be]

and was struck by the lovely fluid color mixing in a short clip near the end (video attached). I’ve not seen fluid color mixing this realistic before and it’s an effect I’ve been wanting to create.

Anyone know where you’d go to find the “custom field advection” mentioned? Not much else is revealed about it.

Thanks,
Joe

There's actually a Houdini help page that covers this effect specifically:
https://www.sidefx.com/docs/houdini/fluid/narrowband.html [www.sidefx.com]

@ziconic
Thank you so much, I've been searching like crazy, never thought to look under “Narrow band”!

Ah, unfortunately the instructions didn’t work as described. I’m guessing some of the nodes have changed since it was written. It’d be great if there was a simple way to mix fluid colors, you’d think it would be an effect that’d be needed often enough to warrant a dedicated node.

The instructions do work but they don't tell you how to take the sim data and produce the final rendered result. In addition to the usual surface volume + fluid particles, you now have a color volume (Cd.*) that you can use to color the interior of your fluid volume to show the mixing effect. I don't actually know the best way to put all these pieces together but if you do figure it out, please share it here.