# Rendering speed slower than "raw" Vtk

**URL:** <https://discourse.slicer.org/t/rendering-speed-slower-than-raw-vtk/7190>\
**Category:** Development\
**Created:** [June 16, 2019, 10:17pm UTC](https://discourse.slicer.org/t/rendering-speed-slower-than-raw-vtk/7190 "2019-06-16T22:17:11Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![klayman](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/klayman/32/3967_2.png) [@klayman](https://discourse.slicer.org/u/klayman)\
**Post date:** [June 16, 2019, 10:17pm UTC](https://discourse.slicer.org/t/rendering-speed-slower-than-raw-vtk/7190/1 "2019-06-16T22:17:11Z")

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Hello, I am loading a CT volume 600x600x312 to slicer4, and playing with the same volume in raw VTK by using a modified Medical4 demo where I use VtkOpenGLGpuMapper (I guess it’s the same I get in slicer4 when I select Vtk GPU raycast), gradient opacity, same colormap as in the slicer4 test, shading disabled in both cases, so all in all should be the same settings.

Question 1: is there a way to share the settings exactly between slicer4 and a VTK c++ program?  
Question 2: Slicer4 is way slower in rendering compared to a bare VTK render window. It’s slower during interaction, almost as if Slicer4 is always rendering full quality, and it’s much slower also in the final renders. Am I missing some settings, or is Slicer4 doing something different than VTK?

Thanks!

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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:** [June 16, 2019, 10:36pm UTC](https://discourse.slicer.org/t/rendering-speed-slower-than-raw-vtk/7190/2 "2019-06-16T22:36:20Z")

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Rendering speed should be exactly the same as in any other VTK-based application.

There might have been a couple of weeks when the 4.11.x preview version always rendered in full quality. Try latest preview version and tune quality settings in Volume rendering module / Advanced / Techniques / Quality and Interactive speed.

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**Author:** ![muratmaga](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/muratmaga/32/3622_2.png) [@muratmaga](https://discourse.slicer.org/u/muratmaga)\
**Post date:** [June 17, 2019, 4:02am UTC](https://discourse.slicer.org/t/rendering-speed-slower-than-raw-vtk/7190/3 "2019-06-17T04:02:01Z")

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I don’t know if it is related or not, but I always have been getting poor rendering performance when the quality is set to adaptive, and had better performance with ‘Normal’ quality.