See attached Exodus file comprised of quadratic hexahedral elements (Hex27). Whenever a non-zero Nonlinear Subdivision Level is used, to show the curved elements, “speckles” appear on the surfaces and the surface edges become “dashed”. The default setting for NSL is 1, so by default these meshes look… unprofessional (i.e. not suitable for publication). Is there a setting that I need to activate in order to properly visualize higher-order meshes in ParaView? This isn’t the first issue I’ve seen with higher-order meshes.
I’m seeing this behavior in ParaView 5.8.1 and ParaView 5.9.0-RC2, Windows 10, NVIDIA 2060 SUPER
The speckling is not an artifact of the JPEG/PNG compression… that is what it actually looks like in ParaView. If I change from Surface with Edges to just Surface mode it all goes away:
A workaround for now is to add a pass through filter like Calculator or AddFieldArrays and then render that as wireframe while rendering the original dataset as surface.
Thanks for looking at this @utkarsh.ayachit . Your workaround works for my immediate “regular” rendering needs. I took a stab at testing your workaround when doing ray-tracing… here’s my same mesh as above, rendering the AddFieldsArray pass-through as a wireframe with Nonlinear Subdivision Level set to 4 and a very small line width (0.025):
We can see that it looks like the ray-tracer is rendering all facets edges when it should look something like this (note - turned NSL to 0 to show layout):
Agreed. Shouldn’t be too hard to do edges correctly.
A longer term but much cooler possibility is to render the non linear cells directly without tesselation. Would make a good Google summer of code project.
Is this the high frequency artifact of screen space antialiasing (SSAA) with rasterization? You could check by turning it off in settings with 5.8/9, or on with 5.7.
It is a known issue (discussed before merging) that can’t be easily resolved with the approach we use to my knowledge. Part of why we suggest limiting line width to smaller values. The cut outs at the end of the line are due to the other triangle of the quad (recall quads are actually rendered as triangles) not drawing that small section of the line which is contained inside it.
Is there a status update regarding this issue rendering high-order meshes in ParaView? We are aware of a 3rd-party presentation happening this week that will talk about “High-order support in VTK/ParaView” and this doesn’t appear to be on the docket to be fixed in 5.10, 5.11, or 5.12.
