Slicing and Cropping allow to view otherwise hidden, inner parts of a volume without tinkering with the transfer function or the data.
Slicing and cropping of a volume rendering is done by a SlicingPlane which is assigned to the Volume. Up to 16 SlicingPlane can be assigned to a volume via the addTargetVolume method. One SlicingPlane can be assigned to unlimited volumes. How those planes interact with the volume is governed by the slicingPlaneEquations property of the volume. The possible exclusive options are:
None, no interaction between planes and volume. The volume will be rendered in full
Cropping, the rendering will be split in half by a intersecting plane. One half will be rendered the other will not. Further intersecting planes may reduce the rendered parts further.
Slicing, only a small slice around the plane will be rendered with full opacity. Multiple intersecting planes will each reveal the area around themselves.
Both, Both Cropping and Slicing are active. The area around the slicing plane will be rendered with zero transparency and bellow it the volume will be rendered regularly.
The SlicingPlane node itself has no geometry. To make it perceivable or allow user interaction it needs to be attached to other nodes. The calculation for the cropping/slicing happen in world space therefore volume and slicing plane transforms can and should be manipulated via the scene graph.