# how to adjust gl\_pointSize when zoom in/out

**URL:** https://discourse.vtk.org/t/how-to-adjust-gl-pointsize-when-zoom-in-out/16137
**Category:** Support
**Tags:** python, code
**Created:** [November 12, 2025, 3:50am UTC](https://discourse.vtk.org/t/how-to-adjust-gl-pointsize-when-zoom-in-out/16137 "2025-11-12T03:50:53Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![Nam\_Le\_Hoang](https://discourse.vtk.org/user_avatar/discourse.vtk.org/nam_le_hoang/32/10358_2.png) [@Nam\_Le\_Hoang](https://discourse.vtk.org/u/Nam_Le_Hoang)
#### Post date: [November 12, 2025, 3:50am UTC](https://discourse.vtk.org/t/how-to-adjust-gl-pointsize-when-zoom-in-out/16137/1 "2025-11-12T03:50:53Z")

</div>

Hi everyone,

I have a problem need the support. I’m using vtk with python using vtkInteractorStyleTrackballCamera with the setting

``  
_self_.interactor\_style = vtk.vtkInteractorStyleTrackballCamera()  
_self_.interactor.SetInteractorStyle(_self_.interactor\_style)  
_self_.interactor\_style.AutoAdjustCameraClippingRangeOff()  
camera = _self_.renderer.GetActiveCamera()  
camera.ParallelProjectionOn()  
```

and display a pointcloud using vtkOpenGLPolyDataMapper with input from vtkVertexGlyphFilter.  
Now I want to adjust the gl\_pointSize using glsl vertextShader, like when zoom in the point becomes bigger. I set SetUseProgramPointSize(True) and tried with many MC..Matrix but didn’t work.  
any help would be appreciated