# failed to convert polydata to volume

**URL:** https://discourse.vtk.org/t/failed-to-convert-polydata-to-volume/10408
**Category:** Support
**Created:** [January 9, 2023, 1:55pm UTC](https://discourse.vtk.org/t/failed-to-convert-polydata-to-volume/10408 "2023-01-09T13:55:08Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![zhang-qiang-github](https://discourse.vtk.org/user_avatar/discourse.vtk.org/zhang-qiang-github/32/2519_2.png) [@zhang-qiang-github](https://discourse.vtk.org/u/zhang-qiang-github)
#### Post date: [January 9, 2023, 1:55pm UTC](https://discourse.vtk.org/t/failed-to-convert-polydata-to-volume/10408/1 "2023-01-09T13:55:08Z")

</div>

I want to convert a polydata to volume, and my reference code is: [https://kitware.github.io/vtk-examples/site/Cxx/PolyData/PolyDataToImageData/](https://kitware.github.io/vtk-examples/site/Cxx/PolyData/PolyDataToImageData/).

My polydata is:

 ![image](https://discourse.vtk.org/uploads/default/original/2X/a/a1bf57270ead6f0378ae1046a835b9852f56c2ed.jpeg)

But the converted imagedata is:

 ![image](https://discourse.vtk.org/uploads/default/original/2X/6/653f25dd0627c4a80be44bcc1507756131478d13.png)

There is some unexpected connection.

The completed code to reproduce my problem is:

```auto
import vtkmodules.all as vtk

import numpy as np

def GenerateMask(poly, origin=None, spacing=[1, 1, 1]):
    import vtkmodules.all as vtk
    mask = vtk.vtkImageData()
    bounds = poly.GetBounds()

    # 计算图像有多大
    dim = [0, 0, 0]
    for i in [0, 1, 2]:
        dim[i] = int(
            np.ceil((bounds[i * 2 + 1] - bounds[i * 2]) / spacing[i])
        )

    mask.SetDimensions(dim)
    mask.SetSpacing(spacing)
    mask.SetExtent(0, dim[0] - 1, 0, dim[1] - 1, 0, dim[2] - 1)
    if not origin:
        origin = [0, 0, 0]
        origin[0] = bounds[0] + spacing[0] / 2
        origin[1] = bounds[2] + spacing[1] / 2
        origin[2] = bounds[4] + spacing[2] / 2
    mask.SetOrigin(origin)
    mask.AllocateScalars(vtk.VTK_UNSIGNED_CHAR, 1)
    mask.GetPointData().GetScalars().Fill(255)

    pol2stenc = vtk.vtkPolyDataToImageStencil()
    pol2stenc.SetInputData(poly)
    pol2stenc.SetOutputOrigin(mask.GetOrigin())
    pol2stenc.SetOutputSpacing(mask.GetSpacing())
    pol2stenc.SetOutputWholeExtent(mask.GetExtent())
    pol2stenc.Update()

    imgStenc = vtk.vtkImageStencil()
    imgStenc.SetInputData(mask)
    imgStenc.SetStencilConnection(pol2stenc.GetOutputPort())
    imgStenc.SetBackgroundValue(0)
    imgStenc.SetReverseStencil(False)
    imgStenc.Update()

    return imgStenc.GetOutput()

reader = vtk.vtkOBJReader()
reader.SetFileName('vessel.obj')
reader.Update()

polydata = reader.GetOutput()

mask = GenerateMask(polydata, spacing=[0.01, 0.01, 0.01])

mapper = vtk.vtkSmartVolumeMapper()
mapper.SetInputData(mask)
mapper.SetBlendModeToMaximumIntensity()
volume = vtk.vtkVolume()
volume.SetMapper(mapper)

renderer = vtk.vtkRenderer()
renderer.AddActor(volume)
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(renderer)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)
iren.Initialize()
iren.Start()

```

And the polydata is upload to github: [https://github.com/zhang-qiang-github/Test](https://github.com/zhang-qiang-github/Test)

How to obtain correctly volume from this polydata? Ang suggestion is appreciated~~~