In a blender armature modifier there is a setting called "Preserve Volume" which basically stops meshes from collapsing on themselves in some bone-related animations. I'm a newbie animator, but I'm aware that there is more to joints+deformations than just checking the preserve volume box and hoping things look good. This is particularly relevant given that some game engines, such as our beloved BabylonJS (also Unity) do not have this feature. So the question here is really what techniques do peo