[petsc-users] Reference element in DMPlexComputeCellGeometryAffineFEM

[Blaise Bourdin]

Hi,

What reference simplex is DMPlexComputeCellGeometryAffineFEM using in 2 and 3D?
I am used to computing my shape functions on the unit simplex (vertices at the origin and each e_i), but it does not look to be the reference simplex in this function:

In 3D, for the unit simplex with vertices at (0,0,0) (1,0,0) (0,1,0) (0,0,1) (in this order), I get J = 1 / 2 . [[-1,-1,-1],[1,0,0],[0,0,1]] and v0 = [0,0,1]

In 2D, for the unit simplex with vertices at (0,0), (1,0), and (0,1), I get J = 1 / 2. I and v0 = [0,0], which does not make any sense to me (I was assuming that the 2D reference simplex had vertices at (-1,-1), (1, -1) and (-1,1), but if this were the case, v0 would not be 0).

I can build a simple example with meshes consisting only of the unit simplex in 2D and 3D if that would help.

Regards,
Blaise



— 
Canada Research Chair in Mathematical and Computational Aspects of Solid Mechanics (Tier 1)
Professor, Department of Mathematics & Statistics
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