From: John Peterson <peterson@cf...>  20100920 18:03:49

On Mon, Sep 20, 2010 at 9:48 AM, yunfei zhu <yzhu2009@...> wrote: > > I noted one of the comments in quadrature_gauss_3D.C, the tetrahedral > quadrature rules are taken from pg. 222 of "The finite element method" vol.1 > ed.5 by Zienkiewicz & Taylor, > so I checked the details in the book. I find that for each of the quadrature > point, there are 4 tetrahedral coordinates and the sum of the weights are > equal to 1. Those are probably barycentric coordinates, one of which is not independent, i.e. (x,y,z,1xyz). We have simply converted those to (x,y,z). I don't have the book in front of me at the moment, so I'm not totally sure, but you can see more about the barycentric coordinates in fe_lagrange_shape_3D.C, around line 78.  John 