CliffieVanR

[BUG] Double-counting of collision hessian in VDB

1

### Bug Description Hi, I've noticed with the latest version of integrator_vdb.py that inside the function VBD_solve_trimesh_with_self_contact_penetration_free the term particle_hessians seems to be added twice - once at the top...

[BUG] Particle contact forces in VDB

2

### Bug Description Maybe I'm missing something, but it looks like the particle self-contact forces and hessians are not being zeroed for every iteration in the non-self contact version of...

### Bug Description Hi, Since the collision response in integrator_vbd.py has been refactored, we're seeing a 50-100% slowdown in overall simulation time. With the example_cloth_self_contact.py test, per-frame sim time gor4es...

I'm not sure I understand how the repulsive force works in evaluate_vertex_triangle_collision_force_hessian. Consider the case where we're computing the repulsive force for a particle in or near contact with a...

[QUESTION] Model for VDB evaluate_dihedral_angle_based_bending_force_hessian

2

Hi, can I ask which paper is used for the bending force implementation in VDB? So far as I can tell, the direction vectors of the forces don't correspond to...

Hi, I'm curious about the use of this function at the end of every sim iteration. Is it intended to prevent large forces accumulating? Would it make sense to also...

In the no-self contact version, I see this: particle_pos = pos[particle_index] particle_prev_pos = pos[particle_index] However, the self-contact-handling version has particle_prev_pos = pos_prev[particle_index] Is the first instance a typo?

[QUESTION] Damping term in VBD

3

Am I correct to think of the damping term in VDB, called 'spring_kd' in the code, is damping both the elastic spring forces *and* the inertial force? # compute damping...

### Bug Description The functionapply_particle_shape_restitution in integrator_xpbd.py is incorrectly writing the velocity deltas to the array indexed by tid. I believe it ought to be particle_index. ### System Information _No...

### Bug Description I've noticed that a trivial cloth simulation in XPBD with no constraints operating other than springs can explode for realistic cloth densities (around 0.15kgm-2). I've enclosed a...