[SOLVED] Counting number of nodes in contact

[twxu]

Hello,

I’m wondering if there is a way to count the number of nodes that are in contact on a surface. I see that on the SOFA GUI (under “Interactions”) there are lines drawn on contact areas, which I believe correspond to the “alarmDist” field of MinProximityIntersection.

1. Is there a way to see a list of those nodes/elements in contact? I found a related matrix called “constraint” (data field under the collision mesh’s Mechanical Object), but this seems to include more nodes than just those in contact.

2. What do the 3 GUI line colors (red, green/blue, white) mean?

Any guidance would be greatly appreciated, thanks!

Example image:
(link in case embedded image fails: https://github.com/thomaswxu/SOFA/blob/main/exampleImages/exampleContactLines.PNG)

[Hugo]

Hi @twxu

Using the GenericConstraintSolver, you can activate the “computeConstaintForces” boolean. This fills the nodal data field “constraintForces”: this vector will have the size of the constraints, i.e. contacts.

Let me know it this helps.

Best wishes,

Hugo

[twxu]

Hi @Hugo,

Thanks very much; I was able to count the exact number of nodes in contact using both the “constraintForces” vector and a BoxROI containing just the contact surface of the object.

I’m just a bit confused on how to interpret the constraintForces vector: specifically, how to use it to calculate contact pressure. Though, that discussion may be better at the other topic: sofa-framework.org/community/forum/topic/measuring-contact-pressure/

In any case I’ll mark this topic as solved; thanks!

[Author]

Posts