# vtkpolydata is black when it is included in vtkVolume

**URL:** https://discourse.vtk.org/t/vtkpolydata-is-black-when-it-is-included-in-vtkvolume/8382
**Category:** Support
**Created:** [April 26, 2022, 2:17pm UTC](https://discourse.vtk.org/t/vtkpolydata-is-black-when-it-is-included-in-vtkvolume/8382 "2022-04-26T14:17:22Z")
**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: [April 26, 2022, 2:17pm UTC](https://discourse.vtk.org/t/vtkpolydata-is-black-when-it-is-included-in-vtkvolume/8382/1 "2022-04-26T14:17:22Z")

</div>

Currently, I want to display `vtkVolume` and `vtkPolyData` in a render. But, the part of `vtkPolyData`, which is covered by `vtkVolume`, is black. Like the following figure:

 ![image](https://discourse.vtk.org/uploads/default/original/2X/d/d19de6a90f70e8529303acc9d55dec7eb0a96149.jpeg)

The line outside of `vtkVolume` is red, which is what I expected. But the part covered by `vtkVolume` is black.

My code is:

```auto
import vtkmodules.all as vtk

reader = vtk.vtkDICOMImageReader()
reader.SetDirectoryName('./data')
reader.Update()

image = reader.GetOutput()
image.SetOrigin(0, 0, 0)
image.SetDirectionMatrix([1, 0, 0, 0, 1, 0, 0, 0, 1])
print(image.GetBounds())

line = vtk.vtkLineSource()
line.SetPoint1(0, 0, 0)
line.SetPoint2(200, 200, 200)
line.Update()

polyMapper = vtk.vtkPolyDataMapper()
polyMapper.SetInputData(line.GetOutput())
polyActor = vtk.vtkActor()
polyActor.SetMapper(polyMapper)
polyActor.GetProperty().SetColor(255, 0, 0)
polyActor.GetProperty().SetLineWidth(5)

volume = vtk.vtkVolume()
vMapper = vtk.vtkGPUVolumeRayCastMapper()
vMapper.SetBlendModeToMaximumIntensity()
vMapper.SetInputData(image)
volume.SetMapper(vMapper)

render = vtk.vtkRenderer()
render.AddActor(volume)
render.AddActor(polyActor)
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(render)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)
iren.SetInteractorStyle(vtk.vtkInteractorStyleTrackballCamera())
iren.Initialize()
iren.Start()

```

How can I turn the line covered by `vtkVolume` to red?