# Generating an opaque volume using volume rendering

**URL:** <https://discourse.slicer.org/t/generating-an-opaque-volume-using-volume-rendering/12528>\
**Category:** Support\
**Tags:** volume, volume-rendering\
**Created:** [July 14, 2020, 1:14pm UTC](https://discourse.slicer.org/t/generating-an-opaque-volume-using-volume-rendering/12528 "2020-07-14T13:14:59Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![mwyburd](https://avatars.discourse-cdn.com/v4/letter/m/dfb087/32.png) [@mwyburd](https://discourse.slicer.org/u/mwyburd)\
**Post date:** [July 14, 2020, 1:14pm UTC](https://discourse.slicer.org/t/generating-an-opaque-volume-using-volume-rendering/12528/1 "2020-07-14T13:14:59Z")

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I have a volume which contains continuous measures of depth and I want an opaque 3D volume rendering. I have thresholded the volume (in the volume module), to remove the background and have used “synchronize with volumes module” in Volume Rendering. However, when I try to adjust the “scalar opacity mapping” it turn the whole volume dark blue.

 ![Screenshot 2020-07-14 at 12.37.07](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/d/0/d00d68b42a1939be7c587cea0691bd0b2fedbb0a.jpeg) ![Screenshot 2020-07-14 at 12.36.48](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/b/4/b4fd157fbda50d784fe40401376cbec555ebf6ac.jpeg)

Operating system: Ubantu  
Slicer version: 4.10.2  
Expected behavior: opaque 3D volume displaying different depths  
Actual behavior: dark blue opaque volume or transparent volume with correct colours

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [July 14, 2020, 1:55pm UTC](https://discourse.slicer.org/t/generating-an-opaque-volume-using-volume-rendering/12528/2 "2020-07-14T13:55:03Z")

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You will always have near-zero values at the edge of the volume, so if you make the opaque then they will occlude all the other colors.

Since you want to display a surface, a surface rendering is more appropriate: faster, higher quality, and you can of course make it opaque without any problems. To render a colored surface:

- export the segment to model
- use “Probe volume with model” module to add a scalar containing the volume’s voxel values
- use Models module Scalars section to enable scalar display, choose colormap, range, optionally threshold