# \[HELP\]VTK vtkGPUVolumeRayCastMapper Not Working Properly on Mac Parallel Desktop Windows (Volume Invisible/Ghost Shadows)

**URL:** https://discourse.vtk.org/t/help-vtk-vtkgpuvolumeraycastmapper-not-working-properly-on-mac-parallel-desktop-windows-volume-invisible-ghost-shadows/16230
**Category:** Support
**Created:** [January 14, 2026, 8:43am UTC](https://discourse.vtk.org/t/help-vtk-vtkgpuvolumeraycastmapper-not-working-properly-on-mac-parallel-desktop-windows-volume-invisible-ghost-shadows/16230 "2026-01-14T08:43:45Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![yujhuang](https://discourse.vtk.org/user_avatar/discourse.vtk.org/yujhuang/32/2821_2.png) [@yujhuang](https://discourse.vtk.org/u/yujhuang)
#### Post date: [January 14, 2026, 8:43am UTC](https://discourse.vtk.org/t/help-vtk-vtkgpuvolumeraycastmapper-not-working-properly-on-mac-parallel-desktop-windows-volume-invisible-ghost-shadows/16230/1 "2026-01-14T08:43:45Z")

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Hi everyone,

I am implementing a volume rendering Interaction feature using **vtkImageData** and **vtkGPUVolumeRayCastMapper** , and it works well on Windows & Normal PCs.  
Until recently, when I try to run it on MacBook Windows（MacBook Pro Parallel Desktop）, the volume displays none in the most circumstances, even if it displays partly the volume sometimes, “ghost shadows“ would be following while rotating the space.

At first, I wonder if it is the parallel desktop or macbook graphics that are not working with vtk Volume rendering. Then I try to use **3D slicer** rendering a Volume, and it works just fine.

Now I realized that there must be something in 3D slicer different from how I coded in terms of volume rendering. One thing can be certain is that my code did not really fully utilize the Mac graphic resources. So, I tried to use **vtkFixedPointVolumeRayCastMapper** (only use CPU) instead of **vtkGPUVolumeRayCastMapper,** it finally displays all on MacBook Windows（MacBook Pro Parallel Desktop）, however, it interactes with unexpectedly high latency.

I am not sure that if my guesses were right: 1️⃣maybe I need to resample this image to lower its resource consumption 2️⃣maybe I need to find the trick(if there is) that how 3D slice smarterly utialized graphic resources in terms of vtk volume rendering.

Help me please!