Convert vtkArray -> vtkPoints?

Support
1

It seems (to me) that the data in vtkArray should be similar to vtkPoints. If I read in data, as a numpy array, and convert it to vtk format like:

pd = vtk.vtkPolyData()
g = numpy_to_vtk(my_nice_array)
pd.SetPoints(g)

This doesn’t work. I can use something like:

...
pts = vtk.vtkPoints()
for x, y, z in my_nice_array:
    pts.InsertNextPoint(x, y, z)

But I was wondering if I could somehow convert the output of numpy_to_vtk to vtkPoints?

2

Hello,

Can you, please, be more specific? “Does’t work” can mean a lot of different unexpected results when it comes to computer graphics.

regards,

Paulo

3

I guess you can do

pd.GetPoints().SetData(numpy_to_vtk(my_nice_array))
4

First, thanks for the replies.

@Paulo_Carvalho, here is the error that I got:

TypeError: SetPoints argument 1: method requires a vtkPoints, a vtkTypeFloat64Array was provided.

@marcomusy, this is the error that statement generates:

AttributeError: 'NoneType' object has no attribute 'SetData'

Here is the code I ran to get that last error:

import vtk
import numpy as np
from vtk.util.numpy_support import numpy_to_vtk
pd = vtk.vtkPolyData()
g = numpy_to_vtk(np.zeros(5))
pd.GetPoints().SetData(g)
5

What do you get when you run

pd = vtk.vtkPolyData()
g = numpy_to_vtk(my_nice_array)
pd.SetPoints(g)

?

6

When you create a vtkPolyData, it is empty, so it has no points:

>>> pd = vtk.vtkPolyData()
>>> pd.GetPoints()
None

And you can’t call SetPoints() with a vtkDataArray, since they’re different types. So what you have to do is create a vtkPoints object from the vtkDataArray, and then call SetPoints().

>>> pd = vtk.vtkPolyData()
>>> points = vtk.vtkPoints()
>>> points.SetData(numpy_to_vtk(my_nice_array))
>>> pd.SetPoints(points)

Also note that the vtkDataArray must have 3 components or else this will fail. So make sure the array has the correct shape.

7

i think the problem is that your polydata is still empty, this works:

import vedo
msh = vedo.Mesh("https://vedo.embl.es/examples/data/apple.ply")
pd = msh.polydata()
pts = msh.points()

import vtk
import numpy as np
from vtk.util.numpy_support import numpy_to_vtk
#pd = vtk.vtkPolyData()
g = numpy_to_vtk(np.zeros_like(pts)+pts*2) # whatever..
pd.GetPoints().SetData(g)

#vedo.show(pd)

you need to set it with a vtkPoints object.

8

I agree with you guys, that the “points” was empty - it just seemed to me like the vtkPoints is conceptually just an array, I was wondering if there was some way to use the vtk.util function numpy_to_vtk to directly load points instead of having to iterate over the rows in the array to add the coordinates … but it looks like the only way to do it is to iterate over the rows.

9

No, it’s not necessary to iterate over the rows. Both my answer and Marco’s answer demonstrate how to create vtkPoints from a numpy array. It just takes two steps.

10

Ok - sorry, I see that now, thanks!

11

I like to wrap the polydata object first

import numpy as np
from vtkmodules.numpy_interface import dataset_adapter as dsa

polydata = dsa.WrapDataObject(vtk.vtkPolyData())
polydata.Points = np.random.random(30).reshape(-1,3)
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