Help creating a ligament

[Giannossk]

Hi and Happy New Year!
I am a 4th-year medical student from Greece, and I want to simulate the liver, stomach, and hepatogastric ligament. I have a problem: I don’t know how to make the ligament attach to the other two 3D meshes and behave like a regular ligament. By this, I mean that the edges of the ligament should remain attached to the surfaces of the liver and stomach, so that when the liver or stomach moves, the ligament stays connected.
I need a helping hand. Thank you in advance!

[bakpaul]

Hello !

There exist multiple ways of imposing the position of subnodes of an object. They are of three types :

1. Weak: using springs we attach them to external points
2. Projective: overwrite the position and/or the velocity of the points
3. Lagrangian: using Lagrangian multiplier, you enforce a strong mathematical constraint over the position.

In my mind, the best way to do what you are asking is to use a Lagrange multiplier. You can take a look at this new scene that should be merged soon in the Sofa repo : https://github.com/bakpaul/TestScenes/blob/f21b5102ee3767b573357e498290a51edadbebad/Experimental/newSofaMain_v0.5.scn#L135

In this line two BilateralConstraint are added do link two object (the logo and the S through a beam that is modeled with BeamAdapter).

HEre is a gif of the final result (the beam is in green, it might be difficult to see...):