Forcefield to prevent interpenetration of meshes

[ScheiklP]

Hi,
I have a simulation case, where two meshes start in contact (some vertices at the exact same location).
I want to essentially simulate collision, without using the collision components (because they crash, if there is collision in the first simulation step).
Is there a component similar to PlaneForceField, but for meshes?

Cheers,
Paul

[alxbilger]

The generic force field for this is PenalityContactForceField. And it is created dynamically by collision models. The collision models then give contact information to the force field. I don't think it is possible to use it alone.
I believe that PlaneForceField is the only one to "detect" interpenetration. And I am of the opinion that it should not exist, and should be replaced by a PlaneCollisionModel.
The crash is not normal. Do you know what goes wrong? Maybe we can try to fix it.

[bakpaul]

No problem ! The names are missleading.

Ok, for me it means simply that you have problems due to the fact that the positions are equals: the contact normals are then only zeros. In the stage of normalizing them, there is a division by zero and then a NaN appears. What I suggest is to first modify the position yourself to add a bit of space between those to enforce non zero normals and a good direction. The problem is that even if the distance in non-zero, you might get positions that will make the contact in the wrong direction, enforcing interpenetration.

[ScheiklP]

That is indeed my current workaround, but depending on the mesh quality, that can become very unstable / ugly very fast. :D

[hugtalbot]

Could you share a ill-case @ScheiklP please? could be interesting to investigate.
Else, have you successfully achieved your FF preventing interpenetration?

[ScheiklP]

Hi @hugtalbot
my first reply to the comments contains an example scene. :)
#5128 (reply in thread)

No, I have not tried to implement the FF. For now, I just shift the "offending vertices" along the negative vertex normals to move them away from each other.

Cheers,
Paul

[hugtalbot]

Hi @ScheiklP

Have you taken a look at the SofaDistanceGrid plugin?
I think this could do it. Keep us posted

Else, I confirm what Alex said : the generic forcefield could be the PenalityContactForceField, but this components computes forces from dynamically-created contact. It is indeed not possible to use it alone.