Trivial Producer Scalars not Visible? (Part of increasing understanding of VTK + Paraview scripting)

ParaView Support
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1

Hi there,

I’m trying to improve my understanding of both paraview and vtk’s python module by generating small point sets and viewing them in paraview using the Trivial Producer. I succeed in getting points drawn to the screen with this code when I use Run Script in paraview, but there’s no clear way to see the scalar data set on the points.

import numpy as np
from paraview.simple import *
import paraview.vtk as vtk
from paraview.vtk.numpy_interface import dataset_adapter as dsa
import paraview.vtk.util.numpy_support as vnp

node = np.array(
        [[0.0, 0.0, 0.0],
         [1.0, 0.0, 0.0],
         [1.0, 1.0, 0.0],
         [0.0, 1.0, 0.0]], dtype=np.float)

NC = cell.shape[0]

points = vtk.vtkPoints()
points.SetData(vnp.numpy_to_vtk(node))
vpoly = vtk.vtkPolyData()
vpoly.SetPoints(points)

# create scalars
s = vtk.vtkFloatArray()
s.InsertTuple1(0,20.0)
s.InsertTuple1(1,30.0)
s.InsertTuple1(2,50.0)
s.InsertTuple1(3,50.0)

vcells = vtk.vtkCellArray()

for i in range(node.shape[0]):
	vcells.InsertNextCell(1)
	vcells.InsertCellPoint(i)

vpoly.SetVerts(vcells)

vpoly.GetPointData().SetScalars(s)
# how to put uGrid into the following codes
view = GetActiveViewOrCreate('RenderView') 


# create a trivial producer to bridge between the VTK object and ParaView
tp = TrivialProducer()
tp.GetClientSideObject().SetOutput(vpoly)

dispaly = Show(tp)

#Interact()

Funnily enough if I use the vtp extractor then I can open a resulting vtp file and see the scalar data, but I’d prefer not to do those several extra steps just to view some small changes in the values I write in the python script.

Here’s what things look like in paraview. I’m unsure if the error that comes up is related to the missing data displayed

image
image1366×768 174 KB

So the question is, how can I use trivial producer to show scalar data on a vtkPolyData object I’ve written from scratch? In a larger sense this question is also asking “what is the preferred way to use vtk and paraview scripting together?”

Thanks for any support on this matter!

2

the error

Name your array

the question is, how can I use trivial producer to show scalar data on a vtkPolyData object I’ve written from scratch?

Yes, but only in built-in mode, not in server mode.

In a larger sense this question is also asking “what is the preferred way to use vtk and paraview scripting together?”

Programmable source/Filter

3

Thank you for the concise yet comprehensive run through of my questions!

Oh woops, yes I was totally expecting something like _Scalars by default but that was wrong. Sure enough adding s.SetName("test") did the trick.

Great I’ll make sure I understand those better as they are the preferred route to make use of python vtk within paraview.

Cheers

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