Internal force in a softbody

[Ehsanizadi]

Dear All,

Does anyone know how to get the forces between to adjacent nodes in a softbody?

I know that there is a linear stiffness in the softbody that acts as a spring stiffness, but multiplication of "change length" to that stiffness wont result in the internal forces.

It seems that particle masses (masses assigned to each nodes) highly affect the behaviour of the soft body.

Ehsan

[Ehsanizadi]

Or where the principles and formulas of the softbody can be found?

For instance, how the bending constrains work, etc.

[Ehsanizadi]

still wondering ...

[benelot]

I do not know your answer, but from what I realized about bullet is that at some point it usually helps to look directly at the code. First check the header for useful methods and then look through the cpp file to see how it is implemented. Sometimes the internal variables are accessible from outside and you just have to learn what you want to access.

[Ehsanizadi]

I did not find any parameter regarding the internal force within softbody.cpp file.

What is very strange to me is that why the amount of mass of soft body affect the behaviour of it and makes it stiffer?!

In all of the formulations of the spring-mass systems (particle based systems for deformable objects), I never faced that mass of points to associate in the "springy" behaviour of the softbody.

A request to Erwin Coumans:
Can you contact "Nathanael Presson", who wrote the soft body code of bullet, and ask him to answer that?
I sent a message to him and asked the question, but I haven't received any feedback yet.