## XDMF2: support for Matrix type

XDMF2 supports the Matrix type, which is of arbitrary length/shape, http://www.xdmf.org/index.php/Xdmf2_Model_and_Format_Archive.

In vtk this would translate into a flattened vector (Only 3x3 matrices are defined as far as I know). XDMF anyways requires/allows to flatten the dimension, i.e. a 3x3 matrix on a 2x2x2 grid has dimensions 2,2,2,9. This works even if the HDF5 dataset has dimensions of 2,2,2,3,3

Attaches is a set of example files to illustrates the situation.

In the current vtk version, the Matrix type is treated as a scalar, i.e. the first 2x2x2 elements are read (reading component 1,2,3,4 from point 1,1,1 etc...). Attached images illustrate the wrong and the correct behavior.

wrong behavior (only scalar, wrong values)

expected behavior (flattened "Matrix" (vector), correct values)