this might be a stupid question but I just cant figure it out:
in Erleben's Thesis pdf, (Page 83 Section 4.9.7)
he says that
* isnt η the number of direction vectors for the discretized friction cone?From previously we know that the contact Jacobian has 1 + η constraints, so it is a
(1 + η)-by-12 dimensional matrix,
* what puzzles me is the bullet and opentissue implementation of this:
they both set only 3 rows maximum of the jacobian matrix, and for the rows concerned with friction they use the tangential directions t1 and t2 directly, what happens to the other rows?!?! i must have undestood sthg in a wrong way!
* what i was expecting is that t1 and t2 are used to make η directions and these equations are then used to fill η jacobian rows, instead only t1 and t2 are used to fill only 2 rows maximum.
* now intuitivly i undestand that 2 directions t1 and t2 are enough to span the whole tangential plane, if yes then y this whole η story? y not just 2 vectors t1 and t2?
can someone explain that to me please? and excuse my stupidity!!