# QVTKOpenglnativewidget lag during zoom operation

**URL:** https://discourse.vtk.org/t/qvtkopenglnativewidget-lag-during-zoom-operation/14940
**Category:** Support
**Tags:** code
**Created:** [December 1, 2024, 4:52pm UTC](https://discourse.vtk.org/t/qvtkopenglnativewidget-lag-during-zoom-operation/14940 "2024-12-01T16:52:51Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Manjunath\_AV](https://discourse.vtk.org/user_avatar/discourse.vtk.org/manjunath_av/32/9403_2.png) [@Manjunath\_AV](https://discourse.vtk.org/u/Manjunath_AV)
#### Post date: [December 1, 2024, 4:52pm UTC](https://discourse.vtk.org/t/qvtkopenglnativewidget-lag-during-zoom-operation/14940/1 "2024-12-01T16:52:51Z")

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I am using QVTKOpenGLNativeWidget to render 3D DICOM data, but I’ve observed significant lag during zoom operations. Each mouse wheel movement takes 3 to 5 seconds to respond, and CPU usage spikes to 90% during the zooming process. Are there any configurations or optimizations I can apply to improve zoom performance?

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### Author: ![LucasGandel](https://discourse.vtk.org/user_avatar/discourse.vtk.org/lucasgandel/32/1831_2.png) [@LucasGandel](https://discourse.vtk.org/u/LucasGandel)
#### Post date: [December 2, 2024, 12:49pm UTC](https://discourse.vtk.org/t/qvtkopenglnativewidget-lag-during-zoom-operation/14940/2 "2024-12-02T12:49:28Z")

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Can you provide more information on the code (VTK classes) used to render the data? Do you use volume rendering to render the 3D volume? Or is it rendered as a slice and using mouse wheel allows for scrolling between slices?  
What is the size of the 3D volume in each dimension?