*Posting here as requested. Original post is in this GitHub issue:
Making a model/mesh into a soft body when that model was imported from glTF yields some strange results. Essentially the model can’t stay stiff (it will crumple like a paper balloon when it interacts with other geometry) and when it sits on a static plane it will constantly twitch. I suspect there is something wrong with how the internal surfaces of the model are marked which causes the model to both not mark its internal areas correctly and also causes it to “collide” with itself; but I’m not actually much of a 3D engine developer so this is just my guess.
There is a sample (mostly put together by BabylonJSGuide) that can be found here: https://www.babylonjs-playground.com/#XY6QF0#4 . Despite the soft body parameters the first “pillow” shaped model that falls gets crushed under the second one and remains crushed, while the second will continue to twitch: . Removing the second model and just having the first one fall results in the same twitching. Other, more complex models seem to collapse in on a single point, or will basically “burst” and collapse into a crumple.
As this issue does not seem to appear when the model is created within BabylonJS, or when imported from some other formats (*sorry, I don’t have a list of the other formats we checked) I suspect this is something specifically related to how glTF models (and probably their internal geometry, specifically) are imported/interpreted and there is no actual problem with any of the code for soft bodies.