Hi,
I am doing some R&D to model robotic arm static deflection using soft bodies with bullet.
During a simple test setup a rod was imported with TetGen, fixed at one end (with several nodes), and measured the other end to see how does gravity/external forces act on it. Interestingly I have found out that while in a gravity field, the change of TotalMass or VolumeMass or TotalDensity properties does not affect the soft body deformation. Indeed gravity has an effect on the soft body, but mass is not related to deflection. If I apply a constant external force on the other hand and I change those parameters, the rod deforms more or less depending on the numbers.
Note: damping, stiffness, size of the rod are constant.
My question to the bullet library developers:
- Does this equation hold? (according to my tests, it does not)
rho=m/V
where rho - density, m - mass of the body, V - volume of the body
- How is gravity related to a soft body in Bullet? (Normally you would expect that while increasing the mass the rod would deform more)
- What is the true difference between TotalMass and VolumeMass?
Also I would be thankful if you guys link a few papers/posts etc. dealing with soft bodies. I spent quite some time to get an understanding of soft bodies, although there is not too much out there.
Any help is appreciated!
Cheers,
Robert