Physics-based clothing squeeze (quick & dirty proof of concept)

I played around a bit, and managed get some pretty cool early results, so I figured I'd share this little tech demo.

I'm detecting the current position of a single GPU sim particle on the clothing (red plus sign), and nearby soft physics joints around that particle (green plus signs). Then I apply a force to each soft physics joint. It's the same force for every joint, just a simple directional force from the position of the cloth particle towards the average position of the nearby joints. 

TittyMagic's breast morphing based on average position of soft joints is playing a pretty big role, making the entire breast morph as force is applied to just a few soft joints.

This shows it's possible squeeze the soft physics mesh when clothing is equipped just by using physics simulation. To make it practical, there's a lot of things to consider:

• it needs to be performant, and it's currently unclear what the cost will actually be for a result that works and looks good
• the force must be applied from different points on the cloth towards the breast (or glute)
• the amount of force needs to distribute smoothly
• the edge of the clothing item (e.g. upper rim of a bra) needs to be detected, and force should not be applied outside of that edge where there's no clothing area

Obviously, this only works if soft physics is enabled. Whether something similar is possible with non-sim clothing, I'm not sure yet - the current WIP depends on GPU sim particle positions.

I'm hoping to combine this system with adjustments to physics parameters on the individual soft joints, possibly applying force to the hard colliders as well. 

Adjusting the main joint physics (like up/down angle target) would be useful as well. How the main joint physics changes could be calculated from the overall amount of force and the general direction of the force.

I'm a bit hyped about this, but let's keep our pants on as there's a lot of work to do!

-everlaster