[MOAB-dev] One more question: TRI3/6

[Jason Kraftcheck]

Wollaber, Allan B. wrote:
> 
> 
> I've noticed that the vertices coming back from a TRI3 or TRI6 element 
> appear to be numbered in the wrong direction (clockwise instead of 
> counterclockwise). For instance, for a TRI3, I get (using a one-based 
> indexing):
> 

This is independent of the MBCN convention.  Or rather, the MBCN 
convention is that the vertices are ordered counterclockwise about the 
normal of the plane of the triangle.  It doesn't impose any requirements 
on the orientation of the plane of the triangle.  I just checked and 
MOAB does appear to retain the triangle orientation from Cubit.  So 
presumably your problematic triangles were generated that way in Cubit.

Cubit will orient the triangles such that their normal is consistent 
with the normal of the geometric surface they are generated on.  For 
example if you create a block in cubit using the command "brick x 1", 
any triangles on surface 1 will have a normal in the +z direction and 
any on surface 2 will have a normal in the -z direction.

- jason