Incorrect Clipping Plane Behavior

Hi all,
I am visualizing a vtkLODProp3D actor using a vtkGPUVolumeRayCastMapper containing two clipping planes in order to display a MIP slab of variable thickness. These clipping plane should be centered around the focal point and shifted +/- half the desired slice thickness.
Our implementation works well except in cases where images were acquired at ‘non-cardinal’ orientations, requiring transformation into the patient LPS coordinate system for display.

As a result, the clipping plane normal vectors for some of our LPS displays are not aligned with the image volume acquisition normal vector.

In these cases, the planes are clearly thicker than they should be - structures more than 5x the assigned slice thickness away from focal point are visible in the displayed thin slab. This is a directional shift - the planes are ‘offset’ relative to the focal point, with one staying close to the focal point and the other some distance away rather than being equidistant from the focal point.

I found this bug where clipping plane coordinates were not being transformed: PolyDataMapper coordinate shift and scale not applied to clipping planes · Issue #2225 · Kitware/vtk-js · GitHub, could something similar be happening for the above actor/mapper classes? We are using Vtk 9.3.0.


For future reference - potential solution found in source code, merge request submitted after consulting with Kitware. See

@dpseiter please need you need to take some action on your MR to move it forward :slight_smile:

Done -