A multi-material segmentation framework which is able to separate a given 3D image into more than two segments is
discussed. First, the original volume image was segmented by 3D thresholding algorithm. Different parts and materials
can be got by setting the appropriate thresholds. Then the segmented parts were filled into a blank 3D image one after
another, and the multi-material segmented image was achieved. Finally, the result was visualized with volume rendering
method. This framework was developed based on the VTK and ITK libraries. An example of head in CT series images
segmented by this approach is presented.