Feature Request: Automatic Smoothing of Quadratic (or higher) Edges
This feature request follows from the blog post and comments here: https://blog.kitware.com/new-vtk-source-for-generating-different-cell-types/.
Request Summary
Implement automatic edge smoothing to permit quadratic (or higher) order element edges to appear appropriately "curved" without the need for the user to manipulate the Nonlinear Subdivision adjustment. This way, quadratic (or higher order) elements will be shown faithfully without user intervention.
Discussion
Individual mesh elements in an analysis code might be first order / linear, second order / quadratic, etc. For 3-D hexahedra, these designations correspond to mesh element types 12 and 25 on pages 480–481 of The VTK User's Guide, 11th Ed. Recognize that linear elements have nodes only at edge ends / vertices and thus may only have planar faces. However, quadratic elements have mid-edge and edge-end / vertex nodes. Thus, quadratic elements may have planar, bilinear, or quadratic faces depending on the position of the mid-edge node relative to the edge-end nodes.
Currently, ParaView (v5.4.0 at the time of writing) permits adaptive refinement of displayed edges under Advanced Properties -> Nonlinear Subdivision Level (NSL). If a quadratic mesh is imported and NSL is set to 0, the model displays as linear (a more-gross representation of the underlying model). If a quadratic mesh is imported and NSL is set to 1, the edge-end and mid-edge nodes are represented but are connected by straight lines. The user must increase NSL manually to see curvature commensurate with a quadratic mesh. See attached example showing various NSL values for an ostensibly cylindrical model.
It is hoped that the automated smoothing (likely, adaptive) can be implemented to remove the need for the user to adjust NSL such that there is not a significant performance penalty. In this way, the underlying mesh representation can be most-easily visualized. The ability for the user to override automated smoothing should be maintained.
CC: @patchett2002