# [vtkusers] vtkWarpVector/vtkGlyph3D array problem

Charles Kind charles.kind at bristol.ac.uk
Fri Dec 29 17:11:26 EST 2017

```Dear Robby,

Below is a function where I warp points back by half a vector in order that
the vector glyph arrow is drawn later on with the center of the vector in
plane. You will note that I create the warp vector field, apply it to the
warp, copy these points to a polydata then extract all relevant arrays and
copy the whole lot back. This may not be the correct way of doing things, I
am just hacking at VTK, but it works. If you designated arrays as vector or
scalar you will need to do that again afterwards.

# Generate warp vectors, these vectors warp the point data
# Warp centers vectors on plane, but warps base geometry
def CenterVectors(self):
numPoints = self.thinPD.GetNumberOfPoints()
mtrans = vtk.vtkFloatArray()
mtrans.SetNumberOfTuples(numPoints)
mtrans.SetNumberOfComponents(3)
mtrans.SetNumberOfValues(3*numPoints)
mtrans.SetName("mtrans")
# Warp of -(1/2)v centers vectors if vector origin is z=0 plane
for x in range(numPoints):
mtrans.SetTuple3(x, \
-self.thinPD.GetPointData().GetAbstractArray('m').\
GetTuple(x)/2, \
-self.thinPD.GetPointData().GetAbstractArray('m').\
GetTuple(x)/2, \
-self.thinPD.GetPointData().GetAbstractArray('m').\
GetTuple(x)/2)
wpd = vtk.vtkPolyData()
wpd.SetPoints(self.thinPD.GetPoints())
wpd.GetPointData().SetVectors(mtrans)
# Warp vector origins
warpVector = vtk.vtkWarpVector()
warpVector.SetInputData(wpd)
warpVector.Update()
# Cast warped points and original vectors into PolyData
warped = vtk.vtkPolyData()
warped.SetPoints(warpVector.GetOutput().GetPoints())
noarrays = self.thinPD.GetPointData().GetNumberOfArrays()
for x in range(noarrays):
.GetAbstractArray(x))
self.thinPD = warped

Luck,

Charlie

--
Sent from: http://vtk.1045678.n5.nabble.com/VTK-Users-f1224199.html
```