Need a way to subdivide nonsimplicies
"Linear" elements that are not simplicies (i.e., triangles or tetrahedra) are not really interpolated linearly. For example, quadrilaterals have quadratic interpolation and hexahedra have cubic interpolation within. This sometimes manifests itself in simplifications that are made. This often comes up when rendering quads (c.f. https://discourse.paraview.org/t/unsymmetric-contour-rendered-by-symmetric-data/4118).
Sometimes the best way to get around these issues is to subdivide the elements. Unfortunately, ParaView does not provide a way to subdivide elements that are not tris or tets, which makes them useless.
One way to solve this problem would be to be able to subdivide quads and hexs (and perhaps other elements) directly. Another approach would be to add an option to the triangulate/tetrahedralize filter to enable the addition of vertices in faces and/or body to better capture the nonlinear interpolation. (See doi:10.1109/TVCG.2006.22 for a thorough discussion on triangulating hexahedra.)