# GPU Ray casting with HIDDENCELLS

**URL:** https://discourse.paraview.org/t/gpu-ray-casting-with-hiddencells/7376
**Category:** Development
**Created:** [June 8, 2021, 12:34pm UTC](https://discourse.paraview.org/t/gpu-ray-casting-with-hiddencells/7376 "2021-06-08T12:34:31Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![jfavre](https://discourse.paraview.org/letter_avatar_proxy/v4/letter/j/b5ac83/32.png) [@jfavre](https://discourse.paraview.org/u/jfavre)
#### Post date: [June 8, 2021, 12:34pm UTC](https://discourse.paraview.org/t/gpu-ray-casting-with-hiddencells/7376/1 "2021-06-08T12:34:32Z")

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I am having difficulty in blanking cells from a vtkImageData because my experience shows that there seems to be an offset of one cell in each direction where [some] cells marked HIDDENCELL are rendered nonetheless. The attached Python script demonstrates that. In the extreme case of marking _all_ cells hidden, I still see 3 planes of semi-transparent data corresponding to the Z-max,Y-max and X-max planes.

 ![raycast](https://discourse.paraview.org/uploads/default/original/2X/a/ae4066cc51eba04ee914e0a1275489bb8a780896.jpeg)  
[pvTestVolumeRenderingGhostArray.py](https://discourse.paraview.org/uploads/short-url/ilegxbnKpaDuk9LvgVhyWVPXhmv.py) (2.5 KB)