How to output the radius from vtkvmtkPolyDataCenterlines

[NeuZhangQiang]

The VMTK tutorial said that the vtkvmtkPolyDataCenterlines can provide the radius of every point. How can I obtain the radius?
I can obtain the points of center lines as following:

    Centerlines = centerlineFilter.GetOutput()
    centerLinePoints = Centerlines.GetPoints()
    voronoiDiagram = centerlineFilter.GetVoronoiDiagram()

    lines = Centerlines.GetLines()
    numberOfLines = lines.GetNumberOfCells()

    points = Centerlines.GetPoints()
    lines.InitTraversal()
    idList = vtk.vtkIdList()

    while lines.GetNextCell(idList):
        n = idList.GetNumberOfIds()

        for id in range(n):

            pointId = idList.GetId(id)
            point = points.GetPoint(pointId)

Even I can obtain the voronoi diagram voronoiDiagram = centerlineFilter.GetVoronoiDiagram(), I don't know how to obtain the radius.

[lassoan]

You can get radius from the centerline extraction filter as point data array in the output polydata. You can set the array name using SetRadiusArrayName before executing the filter.

[NeuZhangQiang]

Thank you very much for your reply. But I still don't know how to obtain the radius. If I know the radius array name: centerlineFilter.SetRadiusArrayName('MaximumInscribedSphereRadius').

How can I obtain the radius? Could you please provide an example? Python or C++ is OK.

For example, I can obtain the point coordinate of center line as:

    while lines.GetNextCell(idList):
        n = idList.GetNumberOfIds()

        for id in range(n):

            pointId = idList.GetId(id)
            point = points.GetPoint(pointId)

How to obtain the radius for each point?

[lassoan]

You can get point data as a numpy array as it is done in this convenience method:

https://github.com/Slicer/Slicer/blob/1ce740cc25e6f22f7a2816767656fd414a5973c7/Base/Python/slicer/util.py#L1262-L1274

[NeuZhangQiang]

I can get the point as:

voronoiDiagram = centerlineFilter.GetVoronoiDiagram()
import vtk
narray = vtk.util.numpy_support.vtk_to_numpy(voronoiDiagram.GetPoints().GetData())

However, the shape of narray is: n*3, and I believe this array is the coordinate of center lines. I still can not obtain the radius.

[lassoan]

You are right, to get point data arrays (not the point coordinates), you need to use a slightly different method: arrayFromModelPointData

https://github.com/Slicer/Slicer/blob/1ce740cc25e6f22f7a2816767656fd414a5973c7/Base/Python/slicer/util.py#L1283-L1293

[NeuZhangQiang]

@lassoan Thank you for your nice reply. Finally, I can obtain the radius.

import vtk
voronoiDiagram = centerlineFilter.GetVoronoiDiagram()
centerlinePoints = vtk.util.numpy_support.vtk_to_numpy(voronoiDiagram.GetPoints().GetData())
radius = vtk.util.numpy_support.vtk_to_numpy(voronoiDiagram.GetPointData().GetArray('MaximumInscribedSphereRadius'))

Hope it may help others.