WIP - Rolling

Good news, everyone! I finally had a break through last night and got rolling to work with the softbody physics. After trying every built in method available with this physics plugin (and getting poor results for all of them) I went down a bit of a rabbit hole and developed my own technique with some custom code.

As I've explained before, every softbody is made up of a bunch of particles that can squish and deform. A long time ago, I got rolling to work in a defunct physics plugin by simply parenting body parts (like head, hands, etc) to these particles for a firm attachment. It was super easy! You might remember this gif from a few years ago.

However, the plugin I currently use does not have this ability since the particles are not real game objects and they only exist in code or in the editor. This makes the plugin much more efficient, but it also limits easy access to the particles. So to attach body parts I use a skeleton embedded inside the softbody with joints to firmly hold all the body parts in place. It works well, but this method does not allow any sort of physics-based rolling, hence why you can only waddle right now. Here's what that setup looks like behind the scenes.

The plugin has some other built in methods to attach things to a softbody, but the results are pretty janky. Body parts often vibrate or detach whenever the softbody is rolling. So I figured it was impossible to get the results I wanted with this plugin. Here's one disappointing test.

In a last ditch effort, I investigated ways to access the particles programmatically and I eventually found a viable method. First, I manually isolate groups of particles for body parts to attach to. Here's a group for the head attachment.

Then some code cycles through all the particles in the group to retrieve their positions and orientations. It averages them all and tells the body part to follow that average position and rotation (plus some offset values to fine tune it). And voila, the body parts stay firmly attached without any fussing or jank! It sounds pretty simple as I type this out, but finally arriving at this solution took a lot of trial and error.

I think the hard part is over now, but there's still a slew of things I need to hook up and fix to make this work with all the other systems in the game. Hopefully that all goes smoothly and I can release the next build in a week or two.