# Why there is a visual dislocation when I show two volume models in a window.

**URL:** https://discourse.vtk.org/t/why-there-is-a-visual-dislocation-when-i-show-two-volume-models-in-a-window/7489
**Category:** Support
**Created:** [December 24, 2021, 2:50am UTC](https://discourse.vtk.org/t/why-there-is-a-visual-dislocation-when-i-show-two-volume-models-in-a-window/7489 "2021-12-24T02:50:25Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![DDS](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/d/ee7513/32.png) [@DDS](https://discourse.vtk.org/u/DDS)
#### Post date: [December 24, 2021, 2:50am UTC](https://discourse.vtk.org/t/why-there-is-a-visual-dislocation-when-i-show-two-volume-models-in-a-window/7489/1 "2021-12-24T02:50:25Z")

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![1](https://discourse.vtk.org/uploads/default/original/2X/1/10541bf69cb385cf136ead64e6214225d8d2ac80.png)  
 ![2](https://discourse.vtk.org/uploads/default/original/2X/0/028aaec0e77212e50ce3368f7472617fc74578ae.png)

These two models have only displacement in the XY direction. But after rotating the view angle, it looks overlapping. How to make it right ?

What below is the codes. I’m a beginner. Thanks for help.

```auto
// Create a vtkImageData object, then copy it and reset its origin.

img_copied->DeepCopy(img);
img_copied->SetOrigin(nDimX, nDimY, 0);

vtkNew<vtkGPUVolumeRayCastMapper> volumeMapper1, volumeMapper2;
volumeMapper1->SetInputData((vtkImageData *)img);
volumeMapper1->SetBlendModeToComposite();
volumeMapper2->SetInputData((vtkImageData*)img_copied);
volumeMapper2->SetBlendModeToComposite();

// vtkVolumeProperty
vtkNew<vtkVolumeProperty> volumeProperty;
volumeProperty->SetInterpolationTypeToLinear();
volumeProperty->SetAmbient(0.4);
volumeProperty->SetDiffuse(0.6);
volumeProperty->SetSpecular(0.2);

// vtkPiecewiseFunction
vtkNew<vtkPiecewiseFunction> compositeOpacity;
compositeOpacity->AddPoint(1, 0.00);
compositeOpacity->AddPoint(2, 1.00);

volumeProperty->SetScalarOpacity(compositeOpacity);

vtkNew<vtkVolume> volume1, volume2;
volume1->SetMapper(volumeMapper1);
volume1->SetProperty(volumeProperty);
volume2->SetMapper(volumeMapper2);
volume2->SetProperty(volumeProperty);

double viewPort[4] = { 0.0, 0.0, 1.0, 1.0 };

vtkNew<vtkRenderer> renderer;
renderer->SetBackground(1.0, 1.0, 1.0);
renderer->SetViewport(viewPort);
renderer->AddVolume(volume1);
renderer->AddVolume(volume2);

vtkNew<vtkRenderWindow> renWin;
renWin->AddRenderer(renderer);
renWin->SetSize(2160, 1440);
renWin->SetWindowName("VolumeMapper");

vtkNew<vtkRenderWindowInteractor> iren;
iren->SetRenderWindow(renWin);
renWin->Render();
iren->Start();

```

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<div class="post-metadata">

### Author: ![DDS](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/d/ee7513/32.png) [@DDS](https://discourse.vtk.org/u/DDS)
#### Post date: [January 7, 2022, 1:06am UTC](https://discourse.vtk.org/t/why-there-is-a-visual-dislocation-when-i-show-two-volume-models-in-a-window/7489/2 "2022-01-07T01:06:57Z")

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Who can give me some advice to solve this problem ?