Export physical parameters like contact forces

[Shamp0o]

Thank you for this amazing piece of software and for open sourcing it.

I'm planning to use your software in an engineering research context. After playing around with it for a bit I was wondering if there is any way to get contact forces and other values like torques, internal foces, positions and velocities resulting from the simulation with the python bindings. I guess latter two can be calculated from the resulting obj files.

[liminchen]

Thanks for your interest in our work! Unfortunately we didn't expose these to the python binding. But all these information should be able to be obtained via certain C++ functions. For example, the contact forces can be obtained by first computing the barrier gradient using Compute_IncPotential_Gradient() in https://github.com/ipc-sim/Codim-IPC/blob/main/Library/FEM/Energy/IPC_ENERGY.h and then divide it by -dt^2.