Potential Bug in vtkAbstractMapper::RemoveAllClippingPlanes() - Missing Modified() Call

omkar · March 6, 2025, 6:30am

Rendering/Core/vtkAbstractMapper.cxx

6732e34cf


      
          {
            if (this->ClippingPlanes == nullptr)
            {
              vtkErrorMacro(<< "Cannot remove clipping plane: mapper has none");
              return;
            }
            this->ClippingPlanes->RemoveItem(plane);
            this->Modified();
          }
          
          void vtkAbstractMapper::RemoveAllClippingPlanes()
          {
            if (this->ClippingPlanes)
            {
              this->ClippingPlanes->RemoveAllItems();
            }
          }
          
          void vtkAbstractMapper::SetClippingPlanes(vtkPlanes* planes)
          {
            vtkPlane* plane;

I have noticed an interesting behavior in the [vtkAbstractMapper::RemoveAllClippingPlanes()](https://github.com/Kitware/VTK/blob/6732e34cf2d607a2835e867e5d8eb530393c37ec/Rendering/Core/vtkAbstractMapper.cxx#L79) method, where the Modified() function is not called, while it is called inside the [vtkAbstractMapper::RemoveClippingPlane(vtkPlane* plane)](https://github.com/Kitware/VTK/blob/6732e34cf2d607a2835e867e5d8eb530393c37ec/Rendering/Core/vtkAbstractMapper.cxx#L68) method.

The absence of the Modified() call in RemoveAllClippingPlanes() seems to cause incorrect shader selection for the actor when all clipping planes are removed. This is in contrast to the RemoveClippingPlane() method, where Modified() is correctly invoked after removing a single clipping plane.

Is there a specific reason why Modified() is not called in RemoveAllClippingPlanes()? Could this potentially be a bug, or is there an intended design choice behind this behavior?

Looking forward to your insights!

ben.boeckel · March 6, 2025, 11:00am

@sankhesh ?