Collision detection for soft bodies

[Jan Bender]

Hi,

the new version of Bullet supports soft bodies. Since I am working on deformable bodies for my own simulation system, I am interested in the collision detection. How does bullet detect the collisions? Do you use a triangle mesh? Can you handle self-collisions? And what about the critical situations, when the soft body is totally pressed together, can you guarantee a stable collision detection in such situations?

Thanks for your help,

Jan

[Nathanael]

Soft body versus soft body use discreet face/vertex collision only, it can handle self collision, but need some decomposition to avoid false positives not implemented yet (see http://gamma.cs.unc.edu/CDCD/, and http://www.cs.unc.edu/~geom/RTRI/i3d08_RTRI.pdf).

The current implementation is very simple, but not robust. For closed mesh, I'm experimenting with deformable signed distance fields, which, provided an well tessellated mesh, guaranty an O(1) collision query, and are very robust.
For open meshes (cloths) , ideas are welcome! .

Soft body versus rigid body use soft body vertice versus a signed distance field build on the fly in rigid body shapes local space (see http://code.google.com/p/bullet/source/ ... parseSDF.h). Very robust and fast.

Nathanael.

[Antonio Martini]

For closed mesh, I'm experimenting with deformable signed distance fields, which, provided an well tessellated mesh, guaranty an O(1) collision query, and are very robust.

distance fields suffer from various artifacts, see for example fig.1 of:

http://www.beosil.com/download/Penetrat ... _VMV04.pdf

cheers,
Antonio