# vtkGPUVolumeRayCastMapper only consider the last label defined in a mask

**URL:** https://discourse.vtk.org/t/vtkgpuvolumeraycastmapper-only-consider-the-last-label-defined-in-a-mask/4386
**Category:** Support
**Created:** [October 9, 2020, 7:16am UTC](https://discourse.vtk.org/t/vtkgpuvolumeraycastmapper-only-consider-the-last-label-defined-in-a-mask/4386 "2020-10-09T07:16:24Z")
**Posts on this page:** 1
**Showing post:** 5

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### Author: ![zandarina](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/z/4af34b/32.png) [@zandarina](https://discourse.vtk.org/u/zandarina)
#### Post date: [October 13, 2020, 6:51am UTC](https://discourse.vtk.org/t/vtkgpuvolumeraycastmapper-only-consider-the-last-label-defined-in-a-mask/4386/5 "2020-10-13T06:51:23Z")

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Hi thank you for answering. I would like to enable the transfer voxel for regions of the mask not intensity values. But it only allows me to define one label the second is ignored. To click one region for example make it red, to click + shift make it green. If I define only the red label it works if I define green and red it does not work. I wonder what it is the reason. Thanks I added the interpolation in my code.

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