# Anaglyph rendering bug?

**URL:** https://discourse.vtk.org/t/anaglyph-rendering-bug/1887
**Category:** Support
**Created:** [October 9, 2019, 2:12am UTC](https://discourse.vtk.org/t/anaglyph-rendering-bug/1887 "2019-10-09T02:12:43Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![dmgroppe](https://discourse.vtk.org/user_avatar/discourse.vtk.org/dmgroppe/32/25_2.png) [@dmgroppe](https://discourse.vtk.org/u/dmgroppe)
#### Post date: [October 9, 2019, 2:12am UTC](https://discourse.vtk.org/t/anaglyph-rendering-bug/1887/1 "2019-10-09T02:12:43Z")

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Hi all,  
I’m trying to render a raycast volume with some polydata (spheres and tubes) in 3D with VTK’s anaglyph functionality. I set the render window’s stereo type to the default red-cyan anaglyph with the SetStereoTypeToAnaglyph method (using the default value of anaglyph color saturation). However, when I render the image, the raycast volume and polydata separate. You can see this in the attached image:

 ![anaglyphBug](https://discourse.vtk.org/uploads/default/original/1X/f96e846e5e57f805b878b4fe20680f6332985562.jpeg)

In the leftmost pane you seem some raycast blobs. In the middle pane are some spheres centered on the blobs and connected by tubes. The rightmost pane is the same as the middle pane but with stereo rendering. You can see that the blobs and spheres are rendered in different locations even though the spheres should be centered on the blobs. Is this a bug, or have I done something wrong?  
flummoxed,  
-David

P.S. I’m using VTK 8.1.1

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### Author: ![lassoan](https://discourse.vtk.org/user_avatar/discourse.vtk.org/lassoan/32/50_2.png) [@lassoan](https://discourse.vtk.org/u/lassoan)
#### Post date: [October 9, 2019, 2:22am UTC](https://discourse.vtk.org/t/anaglyph-rendering-bug/1887/2 "2019-10-09T02:22:51Z")

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I can confirm that this is a bug in vtkGPUVolumeRaycastMapper (I could reproduce it in 3D Slicer). vtkFixedPointVolumeRayCastMapper renders anaglyph stereo views correctly.

I guess these old-school stereo rendering methods don’t get much attention since VTK offers immersive stereo rendering and 6-DOF control if you buy a virtual reality system for a couple of hundred dollars.

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### Author: ![dmgroppe](https://discourse.vtk.org/user_avatar/discourse.vtk.org/dmgroppe/32/25_2.png) [@dmgroppe](https://discourse.vtk.org/u/dmgroppe)
#### Post date: [November 5, 2019, 4:54pm UTC](https://discourse.vtk.org/t/anaglyph-rendering-bug/1887/3 "2019-11-05T16:54:47Z")

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Thanks very much, Andras. VR seems like overkill for my project but if time permits, I’ll look into it.