# Volumerendering asks for help: can roi be cut backwards? 

**URL:** <https://discourse.slicer.org/t/volumerendering-asks-for-help-can-roi-be-cut-backwards/9750>\
**Category:** Support\
**Created:** [January 9, 2020, 6:45am UTC](https://discourse.slicer.org/t/volumerendering-asks-for-help-can-roi-be-cut-backwards/9750 "2020-01-09T06:45:17Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Shicong](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/shicong/32/6562_2.png) [@Shicong](https://discourse.slicer.org/u/Shicong)\
**Post date:** [January 9, 2020, 6:45am UTC](https://discourse.slicer.org/t/volumerendering-asks-for-help-can-roi-be-cut-backwards/9750/1 "2020-01-09T06:45:17Z")

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I asked if the roi-cut of the volumerender-like body could be reversed? making the panel visible outside and invisible inside. I studied the code, or not, thanks for the support, thanks!  
As shown in the following figure, add two lines of code in the red box, or not. ???!  
[pic1|690x354](https://discourse.slicer.org/404)

 ![pic2](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/b/f/bfd74d3344081ec005e12bebedc171afe4659196.png)

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**Author:** ![Shicong](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/shicong/32/6562_2.png) [@Shicong](https://discourse.slicer.org/u/Shicong)\
**Post date:** [January 9, 2020, 7:32am UTC](https://discourse.slicer.org/t/volumerendering-asks-for-help-can-roi-be-cut-backwards/9750/2 "2020-01-09T07:32:59Z")

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vtkmrmlannotationroid pairs like have inside out flag, but also should have outside in flag, but no, is it

 ![pic3](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/2/b/2bfa27271f83c80ead46ab35b708c723b9e15663.png)

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [January 9, 2020, 1:43pm UTC](https://discourse.slicer.org/t/volumerendering-asks-for-help-can-roi-be-cut-backwards/9750/3 "2020-01-09T13:43:59Z")

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We don’t have that feature exposed in the UI. You would need to provide a custom shader something like what’s described below. It’s possible but not integrated in the app.

> <https://github.com/NA-MIC/ProjectWeek/blob/master/PW28_2018_GranCanaria/Projects/MultiVolumeRendering/README.md>

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**Author:** ![Shicong](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/shicong/32/6562_2.png) [@Shicong](https://discourse.slicer.org/u/Shicong)\
**Post date:** [January 10, 2020, 1:59am UTC](https://discourse.slicer.org/t/volumerendering-asks-for-help-can-roi-be-cut-backwards/9750/4 "2020-01-10T01:59:51Z")

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Thank you very much, I wish you a happy working life! 😄