Object-oriented design and implementation of VORTEX - a C++-class library with Tcl-interface for volume visualization

This paper describes the design and implementation of VORTEX, a software package for generating high-quality images depicting shadowed and colored/textured representations of objects inherently present in a volumetric data set. It is realized as a C++-class library, provided with an API, and suited for inclusion in customized programs. Besides, VORTEX features a Tcl-interface allowing for interactive execution or preparation of scripts for calculating longer image sequences (videos) under controlled alteration of the viewing and/or rendering parameters. Specialties of the package include oversampling in image and object space, voxel traversal acceleration, dynamic adaptation of the ray/surface intersections, depth-dependent transparency, higher order gray level gradient approximations, arbitrarily orientable cut planes, and texture-mapped surface colorations. The design of the class library adheres strictly to the object-oriented paradigm which enables easy alteration and/or adaptation of additional classes and objects. The source and header files of the library are extensively documented according to an own scheme allowing for automatic generation of man-pages and Tcl-wrappers for the Tcl-interpreter by means of a suite of proprietary Per1-scripts. A practical application of VORTEX to a brain physiology problem is discussed at the end of the paper.