mRayCastFunction = vtkVolumeRayCastCompositeFunction::New();
mMapper = vtkVolumeRayCastMapper::New();
mMapper->SetVolumeRayCastFunction(mRayCastFunction);
mMapper->AutoAdjustSampleDistancesOn();
mRayCastFunction = vtkVolumeRayCastCompositeFunction::New();
mMapper = vtkVolumeRayCastMapper::New();
mMapper->SetVolumeRayCastFunction(mRayCastFunction);
mMapper->AutoAdjustSampleDistancesOn();