esys-escript

visualize 8-noded quad mesh

Asked by ceguo

Hi everyone,

I used quad8 elements in the simulation and output the results to a vtu file. Now I import it to both ParaView and Mayavi2, the mesh is shown as triangles rather than quads. Is this a problem caused by the output file format or due to the two visualization toolkits don't support 8-node elements?

Ning

Question information

Language:
English Edit question
Status:
Solved
For:
esys-escript Edit question
Assignee:
No assignee Edit question
Solved by:
Bob
Solved:
Last query:
Last reply:

This question was reopened

Revision history for this message
Lutz Gross (l-gross) said : 		#1

VTK which is the back end for Mayavi and parts of ParaView does not directly support Quad8 elements although it can read the elements from VTK input files. I am not sure about the exact internals but from my understanding - which is consistent to your observations - quad8 elements are displayed using triangles.

Revision history for this message
ceguo (hhh-guo) said : 		#2

Thanks Lutz Gross, that solved my question.

Revision history for this message
ceguo (hhh-guo) said : 		#3

Hi all,

Sorry to reopen the thread again. But the ParaView community says ParaView supports the vtk file with quad8 elements and displays in quads rather than triangles. I look into the generated vtu file, the "connectivity" shows only three nodes in each line; and the "types" shows value of 5 (correspond to triangles in vtk). The value of types in vtk for a quad8 element should be 23 indeed. So I'm wondering if this an error caused by my false use or by the generation function "saveVTK" in esys.weipa?

Ning

Revision history for this message
Best Bob (caltinay) said : 		#4

esys.weipa shares code to save VTK and Silo files and due to limitations of support for certain element types, most quadratic types are converted to a type supported by both file types.
As such, there is currently no way to output rec8 elements from escript into VTK.

Cihan

Revision history for this message
ceguo (hhh-guo) said : 		#5

Thanks Cihan Altinay, that solved my question.