To visualize curved element in paraview by using VTKOutput and subdivision

General
1

Hi,

I am using VTKOutput to export a mesh and visualize it in ParaView.

I use curved boundaries and high-order deformation, so I expect the mesh to look curved. To achieve this, I set the parameter subdivision when exporting the mesh and use the featured edges style in ParaView (both in versions 5.11 and 5.13).

A few months ago, this method worked well, as shown in the first picture attached.

First image showing the desired result
First image showing the desired result968×912 21.5 KB

However, recently, using the same method and code, the result has changed. Now, there is a layer of small triangles along each edge, as shown in the second picture.

Second image showing the new issue
Second image showing the new issue1536×698 34.6 KB

Can anyone explain why this is happening?

Any advice will be very appreciated.
Jiashun

from ngsolve import *
from netgen.geom2d import SplineGeometry

maxh = 0.05
order = 4
x0,y0,r0 = 1/4,1/4,1/2

## Generate mesh, working fem spaces
geo = SplineGeometry()
geo.AddCircle((x0,y0),r0,bc="circle")
mymesh = Mesh(geo.GenerateMesh(maxh=maxh))
mymesh.Curve(order)

## Set a simple but high order deformation
fesV = VectorH1(mymesh,order=order)
VExtend = GridFunction(fesV)
VExtend.Set(CF((x**2,y**2)))
Disp = GridFunction(fesV)
Disp.vec.data += BaseVector(0.1*VExtend.vec.FV().NumPy())
mymesh.SetDeformation(Disp)
        
vtk = VTKOutput(ma=mymesh,coefs=[],\
            filename="./test",\
            subdivision=order,legacy=False)
vtk.Do()