# Unsymmetric contour rendered by symmetric data

**URL:** https://discourse.paraview.org/t/unsymmetric-contour-rendered-by-symmetric-data/4118
**Category:** ParaView Support
**Tags:** vtk
**Created:** [April 20, 2020, 2:32am UTC](https://discourse.paraview.org/t/unsymmetric-contour-rendered-by-symmetric-data/4118 "2020-04-20T02:32:25Z")
**Posts on this page:** 1
**Showing post:** 18

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### Author: ![Seweryn](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/s/3ab097/32.png) [@Seweryn](https://discourse.paraview.org/u/Seweryn)
#### Post date: [May 7, 2020, 6:43pm UTC](https://discourse.paraview.org/t/unsymmetric-contour-rendered-by-symmetric-data/4118/18 "2020-05-07T18:43:48Z")

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Looking at what other dedicated finite element visualization software is doing with symmetric quad data I found that they seems to split a quadrilateral into _four_ triangles (instead of only two). It involves creation of additional node at the quad centroid (sum of x coordinates / 4, sum of y coordinates / 4, value at the centroid sum of values at nodes divided by four). I include here two python matplotlib scripts which illustrate this procedure.  
[quad\_2el\_paraview\_quad22tri.py](https://discourse.paraview.org/uploads/short-url/g5TryQ1IGU93tALvA7IWN0pU5NC.py) (1.5 KB)  
[quad\_2el\_paraview\_quad24tri.py](https://discourse.paraview.org/uploads/short-url/h5aeLFCTEeKxZxl73zY1SMwpaOA.py) (2.7 KB)

And below are the plots they are producing:  
 ![quad-2el-paraview_quad22tri](https://discourse.paraview.org/uploads/default/original/2X/9/92197a7ce6f3a4c00ec540d7f87972813bba670f.png)  
 ![quad-2el-paraview_quad24tri](https://discourse.paraview.org/uploads/default/original/2X/e/e609e06ebaf96008882eb9e220839544d0a896a4.png)

Perhaps in Paraview this kind of internal splitting for quadrilateral can be applied?

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