Help with CompoundShape's SoftBody interactions

[flashintv]

I'm having issues where a fast moving CompoundShape made up of ConvexHullShapes has issues making proper interactions with a SoftBody cloth and practically clips through it with cloth slightly being dragged with it. The only partial fixes I have found were:

• increasing the mVertexRadius tenfold for the SoftBody but that makes it so the SoftBody floats off everything it touches,
• increasing the physics' framerate to over 300, which only helps partially as the SoftBodies still clip through the CompoundShape just slower,
• inflating the CompoundShape's mesh to simulate mVertexRadius' collision but only on the compound, results in slightly better interaction but it still clips through it.

The only way for me to have the SoftBody interact with the CompoundShape properly without any of these things above is moving at a very slow speed.
I'm looking for some pointers on how I could fix this issue, thanks.

Video of the CompoundShape going through the Softbody attached:
https://github.com/user-attachments/assets/fa74b227-deed-4329-b8b2-b989f90fe77e

[jrouwe]

If your character is a CompoundShape of ConvexHullShapes then that means that you are updating the CompoundShape every frame to set the new pose of the character. This does not work in a physics simulation as the simulation doesn't see the velocities of the parts of your compound shape. The only way for this to work is to have 1 kinematic body per convex hull and to move it by setting velocities (BodyInterface::MoveKinematic). Even then, there's a pretty big chance that it will not work as the vertices of your soft body seem to be about shoulder length apart. Only the vertices of the soft body collide. The convex hulls of your character seem to be small enough to easily pass between vertices. I suggest using a single kinematic body with a big capsule around the character to push the cloth away and to keep your convex hulls only for interactions that need more detail (e.g. bullets). If you only use the convex hulls for collision detection (and not for the simulation) then you can move the body by setting position / set position for the compound sub parts.

[flashintv]

Thank you for the fast and detailed response, I tried using the body per convex hull and it still resulted in pretty much the exact same behavior, I guess I will stick to the simpler approach of using a capsule, or try subdiving the softbody until it actually collides with the mesh and check how well it performs then - unless there's a way to declare mVertexRadius for per collidable.