Hello, Background: I was going to implement an implicit approach to 3d tetrahedra deformations (first in Matlab then in C++). I need the Jacobian for the partial derivative of force wrt position to do this. I found this paper that gives a method for computing it: http://www-bcf.usc.edu/~jbarbic/BarbicExactCorotationalFEMStiffnessMatrix.pdf The Question: In the report, he defines a 2skew function (to the right of the page). I'm pretty confused on what it means. I think I forgot what skew means from linear algebra - that's probably part of my problem. It sounds like skew symmetric means that a negated matrix is equal to its transpose. What exactly is this 2skew function for?