# Problem generating non-orthogonal structured grid in Python plugin with temporal data
**URL:** https://discourse.paraview.org/t/problem-generating-non-orthogonal-structured-grid-in-python-plugin-with-temporal-data/17233
**Category:** Development
**Tags:** python, vtk
**Created:** [October 6, 2025, 7:55pm UTC](https://discourse.paraview.org/t/problem-generating-non-orthogonal-structured-grid-in-python-plugin-with-temporal-data/17233 "2025-10-06T19:55:39Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@\_Marco](https://discourse.paraview.org/u/_Marco)
#### Post date: [October 6, 2025, 7:55pm UTC](https://discourse.paraview.org/t/problem-generating-non-orthogonal-structured-grid-in-python-plugin-with-temporal-data/17233/1 "2025-10-06T19:55:39Z")
Hi ParaView developers,
I’m developing a Python plugin for ParaView that produces _ **time-evolving datasets** _. The goal is to generate a _ **structured 3D grid with full control of the coordinates** _ (x, y, z), where:
- _ **x and y** _ can have non-uniform spacing (non-orthogonal curvilinear grid),
- _ **z** _ can have non-constant vertical spacing.
I currently have a working plugin that produces a _ **rectilinear grid** _ with temporal scalar fields, inspired by the `TemporalTestDataSource.py` example from ParaView:
[https://gitlab.kitware.com/paraview/paraview/-/blob/master/Examples/Plugins/TemporalTestDataSource/TemporalTestDataSource.py](https://gitlab.kitware.com/paraview/paraview/-/blob/master/Examples/Plugins/TemporalTestDataSource/TemporalTestDataSource.py)
Here’s a summary of what I have implemented:
1. _ **Time management:** _
2. _**Grid generation in `RequestData()`:**_
3. _ **Controls exposed as sliders in the ParaView GUI:** _
4. _ **Observed problem:** _
None of these approaches produces a visible grid in ParaView when embedded in the plugin pipeline. Standalone scripts work fine (e.g., generating a structured grid in pure Python and writing to `.vts`), but embedding it in `***RequestData()***` fails.
_ **Goal:** _ I want a fully working structured grid plugin that:
- Has _ **time-dependent scalar fields** _.
- Allows _ **arbitrary x, y, z coordinates** _ (non-uniform / curvilinear).
- Works immediately in ParaView without external files.
* * *
_ **Plugin sliders explanation:** _
- _ **TimeSteps:** _ controls how many time steps the source produces.
- _ **z Scale:** _ scales the vertical dimension (useful to exaggerate vertical spacing).
- _ **ArrayCount:** _ number of independent scalar arrays generated per timestep.
- _ **Value Offset:** _ shifts the scalar values globally.
* * *
_ **Question to the community:** _
- How can I _**properly generate a vtkStructuredGrid with arbitrary curvilinear coordinates inside `RequestData()`**_, so that it is visible and renders correctly in ParaView?
- Are there special _ **ordering rules for points or dimensions** _ when using structured grids in a plugin?
- Any working minimal example of _ **time-dependent structured grid with non-uniform x/y/z** _ in a Python plugin would be greatly appreciated.
Thanks!
Plugin code skeleton (rectilinear working version):
> from paraview.util.vtkAlgorithm import \*
> import vtk
> import numpy as np
> from vtkmodules.util import numpy\_support
>
> @smproxy.source(name=“TimeSourceStructured”,
> label=“Time Source Structured Grid with Scalars”)
> class TimeSourceStructured(VTKPythonAlgorithmBase):
> def **init** (self):
> VTKPythonAlgorithmBase. **init** (self,
> nInputPorts=0, nOutputPorts=1,
> outputType=‘vtkRectilinearGrid’)
>
> ```auto
> self.nx, self.ny, self.nz = 115, 85, 32
> self._numOfValues = 10
> self._numOfArrays = 2
> self._valueOffset = 0.0
> self._zscale = 1.0
>
> def _get_timesteps(self):
> return np.arange(self._numOfValues, dtype=np.float64)
>
> def RequestInformation(self, request, inInfoVec, outInfoVec):
> outInfo = outInfoVec.GetInformationObject(0)
> timesteps = self._get_timesteps()
> outInfo.Set(vtk.vtkStreamingDemandDrivenPipeline.TIME_STEPS(), timesteps, len(timesteps))
> outInfo.Set(vtk.vtkStreamingDemandDrivenPipeline.TIME_RANGE(), [timesteps[0], timesteps[-1]], 2)
> return 1
>
> def _get_current_time(self, outInfo):
> timesteps = self._get_timesteps()
> if outInfo.Has(vtk.vtkStreamingDemandDrivenPipeline.UPDATE_TIME_STEP()):
> return outInfo.Get(vtk.vtkStreamingDemandDrivenPipeline.UPDATE_TIME_STEP())
> else:
> return timesteps[0]
>
> def RequestData(self, request, inInfoVec, outInfoVec):
> outInfo = outInfoVec.GetInformationObject(0)
> nx, ny, nz = self.nx, self.ny, self.nz
>
> x_coords = np.linspace(0, nx-1, nx, dtype=np.float32)
> y_coords = np.linspace(0, ny-1, ny, dtype=np.float32)
> z_coords = self._zscale * np.linspace(0, nz-1, nz, dtype=np.float32)
>
> vtk_x = numpy_support.numpy_to_vtk(x_coords, deep=True)
> vtk_y = numpy_support.numpy_to_vtk(y_coords, deep=True)
> vtk_z = numpy_support.numpy_to_vtk(z_coords, deep=True)
>
> grid = vtk.vtkRectilinearGrid()
> grid.SetDimensions(nx, ny, nz)
> grid.SetXCoordinates(vtk_x)
> grid.SetYCoordinates(vtk_y)
> grid.SetZCoordinates(vtk_z)
>
> t = self._get_current_time(outInfo)
>
> gx, gy, gz = np.meshgrid(x_coords[:-1]+0.5, y_coords[:-1]+0.5, z_coords[:-1]+0.5, indexing='ij')
> gx, gy, gz = gx.ravel(), gy.ravel(), gz.ravel()
>
> for k in range(self._numOfArrays):
> arr = np.sin(0.2*t + 0.1*k + 0.05*gx + 0.05*gy + 0.05*gz)
> vtkarr = numpy_support.numpy_to_vtk(arr, deep=True)
> vtkarr.SetName(f"Array_{k}")
> grid.GetCellData().AddArray(vtkarr)
> if k == 0:
> grid.GetCellData().SetScalars(vtkarr)
>
> time_array = vtk.vtkDoubleArray()
> time_array.SetName("TIME")
> time_array.SetNumberOfTuples(1)
> time_array.SetValue(0, t)
> grid.GetFieldData().AddArray(time_array)
>
> output = self.GetOutputData(outInfoVec, 0)
> output.ShallowCopy(grid)
> output.GetInformation().Set(output.DATA_TIME_STEP(), t)
> return 1
>
> @smproperty.intvector(name="TimeSteps", default_values=10)
> @smdomain.intrange(min=1, max=50)
> def SetSteps(self, x):
> self._numOfValues = x
> self.Modified()
>
> @smproperty.doublevector(name="z Scale", default_values=1)
> @smdomain.doublerange(min=1.e-6, max=2)
> def SetScale(self, x):
> self._zscale = x
> self.Modified()
>
> @smproperty.intvector(name="ArrayCount", default_values=2)
> @smdomain.intrange(min=1, max=10)
> def SetArrayCount(self, x):
> self._numOfArrays = x
> self.Modified()
>
> @smproperty.doublevector(name="Value Offset", default_values=0.0)
> def SetOffset(self, x):
> self._valueOffset = x
> self.Modified()
>
> @smproperty.doublevector(name="TimestepValues", information_only="1", si_class="vtkSITimeStepsProperty")
> def GetTimestepValues(self):
> return self._get_timesteps()
>
> ```
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [October 7, 2025, 8:52am UTC](https://discourse.paraview.org/t/problem-generating-non-orthogonal-structured-grid-in-python-plugin-with-temporal-data/17233/2 "2025-10-07T08:52:12Z")
Hi Marco
> [@\_Marco](#):
>
> How can I _**properly generate a vtkStructuredGrid with arbitrary curvilinear coordinates inside `RequestData()`**_
Just create a correct vtkStructuredGrid and it will show up correctly in ParaView
> Are there special _ **ordering rules for points or dimensions** _ when using structured grids
Points should indeed be ordered correctly:
> **[VTK: vtkStructuredGrid Class Reference](https://vtk.org/doc/nightly/html/classvtkStructuredGrid.html)**
---
### Author:  [@\_Marco](https://discourse.paraview.org/u/_Marco)
#### Post date: [October 7, 2025, 2:04pm UTC](https://discourse.paraview.org/t/problem-generating-non-orthogonal-structured-grid-in-python-plugin-with-temporal-data/17233/3 "2025-10-07T14:04:41Z")
Hi Mathieu,
Thank you so much for replying at the speed of light and for the link.
I have followed that and have come across a almost python-ready example:
[https://examples.vtk.org/site/Python/StructuredPoints/Vol/](https://examples.vtk.org/site/Python/StructuredPoints/Vol/)
I have simplified down the code to a bare minimum for testing. Now my RequestData is:
```auto
def RequestData(self, request, inInfoVec, outInfoVec):
from vtkmodules.vtkCommonDataModel import vtkStructuredGrid
from vtkmodules.vtkCommonCore import vtkPoints, vtkDoubleArray
# --- Get the output from ParaView ---
output = vtkStructuredGrid.GetData(outInfoVec, 0)
# --- Grid dimensions ---
dims = [13, 11, 11]
output.SetDimensions(dims)
# --- Points and scalars ---
numPts = dims[0]*dims[1]*dims[2]
points = vtkPoints()
points.SetNumberOfPoints(numPts) # Must set number of points
scalars = vtkDoubleArray()
scalars.SetName("MyScalars")
scalars.SetNumberOfTuples(numPts)
# --- Fill grid ---
offset = 0
for k in range(dims[2]):
z = -1.0 + k
for j in range(dims[1]):
y = -1.0 + j
for i in range(dims[0]):
x = -1.0 + i
points.SetPoint(offset, x, y, z)
scalars.SetTuple1(offset, x **2 + y** 2 + z**2)
offset += 1
# --- Assign to output ---
output.SetPoints(points)
output.GetPointData().SetScalars(scalars)
return 1
```
As before, the output when initializing is indeed a `vtkstructuredGrid`:
`def __init__ (self): VTKPythonAlgorithmBase. __init__ (self, nInputPorts=0, nOutputPorts=1, outputType='vtkStructuredGrid')`
I see the actual variable and variable name in the dropdown menu.
I can see the colorbar showing up, with right value range.
The inspector tab is telling me everything looks nice, but when debugging:
`Number Of Points: 0`
`Bounds: Xmin,Xmax: (1e+299, -1e+299)`
What am I doing wrong?
I tried all day without managing to get a grip on what I might be doing wrong, but I smell I am very close…
---
### Author:  [@mwestphal](https://discourse.paraview.org/u/mwestphal)
#### Post date: [October 8, 2025, 6:02am UTC](https://discourse.paraview.org/t/problem-generating-non-orthogonal-structured-grid-in-python-plugin-with-temporal-data/17233/4 "2025-10-08T06:02:26Z")
> [@\_Marco](#):
>
> when debugging:
>
> ``
When is NumberOfPoints 0 ?
You seem to fill the points correcty.
---
### Author:  [@jfavre](https://discourse.paraview.org/u/jfavre)
#### Post date: [October 8, 2025, 6:17am UTC](https://discourse.paraview.org/t/problem-generating-non-orthogonal-structured-grid-in-python-plugin-with-temporal-data/17233/5 "2025-10-08T06:17:09Z")
try this out:
[vtkStructuredGrid.py](https://discourse.paraview.org/uploads/short-url/bE43LYsXbivyVkFAABnvbI56wLn.py) (1.8 KB)
---
### Author:  [@\_Marco](https://discourse.paraview.org/u/_Marco)
#### Post date: [October 8, 2025, 10:27am UTC](https://discourse.paraview.org/t/problem-generating-non-orthogonal-structured-grid-in-python-plugin-with-temporal-data/17233/6 "2025-10-08T10:27:42Z")
Dear Jean,
My gratitude for this. It is a splendid, basic and WORKING MWE I can use to start building upon.
It might be likely I will come back here to ask more questions.
Kind regards,
Marco