cylindrical_filter.py

#input type: points with data associated with them
#output type: vtkUnstructuredGrid
# example of unstructured programmable filter
# gist -u  85478f5ea04b9d2db6f1 cylindrical_filter.py
#https://gist.github.com/85478f5ea04b9d2db6f1

# place in script box:
from paraview import vtk
import numpy as np

def coord_transform(x,y,z,Rmax):
    rhoact = np.sqrt(x*x + y*y + z*z)
    theta = np.arctan(z/np.sqrt(x*x + y*y))
    thetay = np.arctan2(y,x)
    z = Rmax * np.tan(theta)
    rhotot = np.sqrt(z*z + Rmax*Rmax)
    rhothick = rhotot - rhoact
    #sf = (Rmax - rhothick)/np.sqrt(x*x + y*y)
    #x = sf*x
    #y = sf*y
    x = (Rmax - rhothick)*np.cos(thetay)
    y = (Rmax - rhothick)*np.sin(thetay)
    
    return x, y, z


pdi = self.GetInput()
pdo =  self.GetOutput()

newPoints = vtk.vtkPoints()
numPoints = pdi.GetNumberOfPoints()

ivals = pdi.GetPointData().GetArray(0)

#elev = vtk.vtkFloatArray()
#elev.SetName('elevation')
#elev.SetNumberOfComponents(1)
#elev.SetNumberOfTuples(numPoints)

Rmax = 0.0
for i in range(0, numPoints):
    coord = pdi.GetPoint(i)
    x, y, z = coord[:3]
    Rmax = np.maximum(0.0,np.sqrt(x*x + y*y ))

for i in range(0, numPoints):
    coord = pdi.GetPoint(i)
    x, y, z = coord[:3]
    #elev.SetValue(i, z)
    # coodinate transform
    x, y, z = coord_transform(x,y,z,Rmax)
    newPoints.InsertPoint(i, x, y, z)
pdo.SetPoints(newPoints)

pdo.GetPointData().AddArray(ivals)
#pdo.GetPointData().AddArray(elev)

print 'finished with coordinate transform!'