WIP #44: Sticky Bunny

Those of you who've ben reading these for a while will remember my experiments last year with Goo, and if you've been following these animations for a while you'll have noticed that I've experimented with various different forms of "sticky sloppy strings" all the way back since 2021. Well, check this out:

So what's the big deal? You've done this already! While I've got some good results before, you may have noticed that I didn't really use those techniques again very much on subsequent animations. That's for a few reasons, but the main one is that I never found a technique that was particularly flexible. Curves and hooks, bendy bones, shrinkwrap and surface deform are all powerful tools, but the use case of arbitrarily numerous and complex sticky strings they actually reach their limits one way or another before they really deliver anything truly "satisfactory" from a workflow development perspective. Or, to put it another way, those techniques worked well in that one animation where I used them, but they weren't going to work for the next one, or the one after that. The other major dealbreaker with those other techniques are extremely manual, and not in a fun way. I hate animating with hooks, and I hate having to re-do all the same setup for each new bit of sloppy goodness I add, it really discourages the whole approach.

This technique is different! behold, the secret sauce:

It's a deformer mesh! Anyone who's followed lewdineer's tutorials for jiggle physics will be familiar with this approach, except here we're not doing any simulation, and the binding method is very different, so it's only similar in general principle. What this is, is a simple cylinder that's surface deformed to their bodies (each end of the cylinder is separated by a vgroup, and assigned to a separate surface deform modifier). The great thing about this is that the bind data is stored in the surface deform modifier, so the original cylinder can still be accessed! This isn't mission critical, but it's a nice bonus for visualizing what the hell is actually going on when things get cramped:

So now we have a problem. The liquid needs to be animated stretching out and breaking, but if we use surface deform it'll override any shape keys, and mesh deform also won't work since while it doesn't freeze the mesh, it does create an extremely awkward layering of vertex transformations that rapidly makes everything impossible to work with.

Are we out of options? Hell no, we just have to use geometry nodes! and look at that, I've already made the node graph for this, we're using UV Reprojection! If you download that node graph, just bear in mind it's not going to be plug-and-play for this, but it's close. All we need the geo nodes to do is to transform the goop meshes into the local UV space of our target mesh and bippity boppity boop, it just works!

But here's the real advantage of doing it this way, the actual liquid shapes and animations are completely free-form, and they can be added and removed very easily! that means we can make the shapes as complex as we like, move them around on the fly, and add more wherever we please!

Finally, a technique that I can actually reccomend! Once I get some time, I intend to package it up into a nodegroup and tutorial that I can put up for download somewhere, but in the mean time I hope this is enough that if you want to you can try it yourself!