WIP #25: True Goo (Patreon)

Gather 'round everyone! This one's a big deal. As those of you who've read part 1, part 2 and part 3 of my "sticky diaries" will know, really good looking spooge has been a bit of a white whale of mine. Specifically it's a sperm whale, I guess.

Well, most of that experimentation, and the techniques I used on Study Break, were explicitly conceived to avoid using fluid simulation, because it's bad (I'm sure you've all seen the rather janky, jittering and globby attempts floating around out there) - but I pose to you this question, what if instead of being bad, fluid simulation could be... good? Don't get it twisted, mantaflow is still pretty terrible, especially in this use case, but allow me to introduce: the flip fluids addon! It's a totally different fluid solver, although it uses some of the same core principles as mantaflow, which is far more stable, accurate and easy to work with - plus it has proper viscosity, friction and surface tension behaviour!

There are a handful of other creators using the addon - I first saw it in use by polished jade bell and thought, huh, I know that isn't possible in blender by default. So I bought the addon and, goodness! It's kind of just solved 90% of my problems. The Nut is possible now.

Here's an initial render from just 20 minutes of setting up and testing:

As you can see, even without much refinement, the result is pretty amazing out of the box! It is telling, though, that going from this early example to the final result you see above took about a week and a half of experimentation and well over 50 hours of baking. Nothing comes for free.

 So did I waste my time with the previous research? Not at all! For one thing, I learned a lot, and that kind of knowledge about solving weird janky edge cases in blender is almost infinitely useful. More importantly though, the addon isn't perfect: 

- For one thing the consistency is more dribbly than I'd like, it tends to form very long, thin, flowing strings that aren't accurate to the substance in real life - this is likely to be a function of insufficient surface tension, which is computationally expensive. 

- Perhaps the biggest thing though: while the friction is there, proper stickiness is still not. There are some options within the addon (having the collision mesh double as a surface attractor force field seems to produce some very nice results, with the added benefit of good volume preservation!), but also my previous techniques with geometry nodes and dynamic paint can be used to produce a thin film of "residue" left behind on every surface the substance touches. The main issue is performantly generating that residue mesh at the kind of resolution that's required to support the crazy detail fidelity the fluid sim can provide. It might also be possible to use this to model a kind of "hydrophobic" effect of dry skin. I'll have to do more experimentation.

There's also the possibility of harnessing the "whitewater" system present in the flip fluids addon to have things like bubbles! I couldn't get it to behave with this example, but that won't deter me :D

Until next time, and expect more regular goop in upcoming animation! 

PS - Also, this essentially allows me to offer things like creampies, facials etc in commissions at like 1/5 the price and double the complexity. For anyone who might be interested in that ;)