Partitioned volume (ParVo) rendering approach which was used for creating 3D illustrations and animations of the Visible Human™ and Visible Embryo™ datasets. This approach is one of the key features of this powerful software toolkit called etdips (exploratory Two/Three Dimensional Image Processing System). An interactive graphical user interface (GUI) for ParVo in TDIPS offers simple mouse-based manipulation for numerous volume rendering parameters. Interactive dialogs and graphical feedback allow accurate specification of the rendering transfer function, viewpoint parameters, lighting controls, object rotation, and volume of interest. The color and opacity values of the transfer function are specified using direct modification of nodes on a 2D graph. Four light sources can be specified, with independent control of their location, intensity, color, attenuation, and specular parameters based on the Phong lighting model. Other controls for selecting back-to-front or front-to-back compositing, modifying the sampling period, and over-sampling are also provided. Furthermore, the system also offers an animation utility based on key-frames. It allows the user to specify and interactively manipulate all the rendering parameters at each key-frame, and generates a log file for batch processing of vast datasets and long animations.

Aside from volume rendering, etdips contains a rich set of 3D image processing and manipulation tools. These include volume analysis (3D dilation and erosion, edge detection - Zucker-Hummel/Sobel, multivalue thresholding, conditional averaging), logical and binary operations (and, or, not, bit-shifts), data reformatting (interpolation, volume-of-interest, downsampling), 3D convolution filtering, skeleton-climbing error-free iso-surface rendering, statistical measurements, volume conversion, and sub-volume manipulation options. This system also has a simple command line interface which allows inter- and intra-volume processing of multiple volumes using symbolic names. etdips has an Object-Oriented Design with a multi-level Application Programming Interface (API): the application development interface, algorithm development interface, and the command-line interface. This design significantly adds to the feature set by offering complete flexibility, expandability, and portability. Currently, the system runs on Windows 2000/NT/9x workstations with OpenGL.