AN IMPORTANT GOAL IN VOLUME RENDERING, especially when we aredealing with medical data, is to be able to visually separate and selectively enable or disable specific objects of interest contained in a single volumetric data set. As we have seen in Chapter 15, cutaway views and general volumetric clipping very effectively allow parts of the volume to be removed during rendering that would otherwise occlude interesting areas. Rendering segmented volume data can be seen as an extension of volume clipping with a voxelized selection volume as described in Chapter 15.