How did you create the vtk files in python?

[ricky2208]

I am trying to create a 3D dataset (I do not want to use existing) using python.
The output will be a vtk structured data format.
The size of the dataset is user input (currently I am trying with 216*216) over a domain from -50.0 to 50.0 in a. I am calculating the scalar value at each grid location by the circle formula sqrt(xx + yy + zz)
I have written the following code but it seems to be incorrect as no file is being generated.
import vtk
import math
x=0
y=0
z=0
print("enter size of the dataset ")
limit=int(input())
for i in range(0,limit):
for j in range(0,limit):
for k in range(0,limit):
x=i
y=j
z=k
vol=math.sqrt(pow(x,2)+pow(y,2)+pow(z,2))
w=vtk.vtkDataSetWriter()
w.SetFileName('C:/Users/prakhyati/datafile1.vtk')
w.Update()
w.Write()

[marcomusy]

Your code is not quite right.
try this:

pip install --upgrade vtkplotter

from vtkplotter import Plotter, sqrt
from vtkplotter.utils import pointScalars


print("enter size of the dataset ")
#limit=int(input())
limit=20

vp = Plotter()

grid=[]
scalars=[]
for i in range(0,limit):
    for j in range(0,limit):
        for k in range(0,limit):
            vol = sqrt(pow(i,2)+pow(j,2)+pow(k,2))
            scalars.append(vol)
            grid.append([i,j,k])

act = vp.points(grid)

pointScalars(act, scalars, 'myscalars')

vp.write(act, 'myfile.vtk')

vp.show()

#to visualize, at command line:
# > vtkplotter myfile.vtk  # (then press p and k)

[ricky2208]

can we do it without using vtkplotter
I tried yesterday and wrote this

import vtk
import math
fname='C:/Users/prakhyati/datafile1.vtk'
print("enter size of the dataset ")
limit=int(input())
xAxis = -50.0
yAxis = -50.0
zAxis = -50.0
domain=50
width=0
scalar = "volume"
Points = vtk.vtkPoints()
for i in range(0,limit):
xAxis=xAxis+width
for j in range(0,limit):
yAxis=yAxis+width
for k in range(0,limit):
zAxis=zAxis+width
width=((2*domain)/limit)
vol = math.sqrt(pow(xAxis, 2) + pow(yAxis, 2) + pow(zAxis, 2))
Points.InsertNextPoint(xAxis,yAxis,zAxis)
polydata = vtk.vtkPolyData()
polydata.SetPoints(Points)

        if vtk.VTK_MAJOR_VERSION <= 5:
            polydata.Update()
        writer = vtk.vtkPolyDataWriter()
        writer.SetFileName(fname)
        writer.SetFileFormat(1,2)
        if vtk.VTK_MAJOR_VERSION <= 5:
            writer.SetInput(polydata)
        else:
            writer.SetInputData(polydata)
        writer.Write()

It does create the file, but I am unable to add scalars (can't find set scalar function for polydata )
Also, I have doubt if I am calculating the coordinates of the grid correctly (I did this on pen and paper and implemented, domain is from -50.0 to 50.0)
Any information on the same will be a help.

[marcomusy]

I really wonder why you would not use the package.

Anyway you can find hints in vtkplotter/utils.py (pointScalars() method).