# Major slice scrolling performance degradation with volume rendering on

**URL:** <https://discourse.slicer.org/t/major-slice-scrolling-performance-degradation-with-volume-rendering-on/938>\
**Category:** Support\
**Tags:** performance\
**Created:** [August 24, 2017, 6:04pm UTC](https://discourse.slicer.org/t/major-slice-scrolling-performance-degradation-with-volume-rendering-on/938 "2017-08-24T18:04:18Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![fedorov](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fedorov/32/14_2.png) [@fedorov](https://discourse.slicer.org/u/fedorov)\
**Post date:** [August 24, 2017, 6:04pm UTC](https://discourse.slicer.org/t/major-slice-scrolling-performance-degradation-with-volume-rendering-on/938/1 "2017-08-24T18:04:18Z")

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There appears to be order of magnitude (from ~15 ms/frame to ~150 ms/frame) degradation in slice scrolling performance when volume rendering is enabled (slice is not shown in 3d view).

See demo in this screencast: [https://www.screencast.com/t/fJ9O9N2El](https://www.screencast.com/t/fJ9O9N2El)

This was done on a mac with the latest nightly.

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**Author:** ![jcfr](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jcfr/32/17825_2.png) [@jcfr](https://discourse.slicer.org/u/jcfr)\
**Post date:** [August 24, 2017, 6:43pm UTC](https://discourse.slicer.org/t/major-slice-scrolling-performance-degradation-with-volume-rendering-on/938/2 "2017-08-24T18:43:33Z")

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Are you able to reproduce the problem when building against Qt5 ? (which will enable VTK8 and the latest OpenGL backend)

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**Author:** ![fedorov](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fedorov/32/14_2.png) [@fedorov](https://discourse.slicer.org/u/fedorov)\
**Post date:** [August 24, 2017, 6:47pm UTC](https://discourse.slicer.org/t/major-slice-scrolling-performance-degradation-with-volume-rendering-on/938/3 "2017-08-24T18:47:49Z")

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I can try this after Friday (or Friday afternoon).

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**Author:** ![fedorov](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fedorov/32/14_2.png) [@fedorov](https://discourse.slicer.org/u/fedorov)\
**Post date:** [August 24, 2017, 6:48pm UTC](https://discourse.slicer.org/t/major-slice-scrolling-performance-degradation-with-volume-rendering-on/938/4 "2017-08-24T18:48:29Z")

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The reason you get all those reports from me is that I am preparing for a tutorial, which I plan to dry-run tomorrow morning, and I report things as they show up … I hope this is helpful.

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**Author:** ![jcfr](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jcfr/32/17825_2.png) [@jcfr](https://discourse.slicer.org/u/jcfr)\
**Post date:** [August 24, 2017, 7:33pm UTC](https://discourse.slicer.org/t/major-slice-scrolling-performance-degradation-with-volume-rendering-on/938/5 "2017-08-24T19:33:31Z")

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> [@fedorov](#):
>
> I am preparing for a tutorial, which I plan to dry-run tomorrow morning, and I report things as they show up

That is great. Then, we will be in good shape for the next release

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**Author:** ![chir.set](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/chir.set/32/66982_2.png) [@chir.set](https://discourse.slicer.org/u/chir.set)\
**Post date:** [August 25, 2017, 6:28am UTC](https://discourse.slicer.org/t/major-slice-scrolling-performance-degradation-with-volume-rendering-on/938/6 "2017-08-25T06:28:10Z")

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The performance drop is the same in Qt5. If ‘Quality control’ is set to maximum, it’s even more noticeable.

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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:** [August 25, 2017, 1:46pm UTC](https://discourse.slicer.org/t/major-slice-scrolling-performance-degradation-with-volume-rendering-on/938/7 "2017-08-25T13:46:06Z")

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I’ve entered a ticket to track the resolution of this issue:  
[https://issues.slicer.org/view.php?id=4423](https://issues.slicer.org/view.php?id=4423)