The Visualization Toolkit (VTK) is an open-source, freely available software system for 3D computer graphics, modeling, image processing, volume rendering, scientific visualization, and information visualization. VTK also includes ancillary support for 3D interaction widgets, two- and three-dimensional annotation, and parallel computing. At its core, VTK is implemented as a C++ toolkit, requiring users to build applications by combining various objects into an application. The system also supports automated wrapping of the C++ core into Python, Java, and Tcl, so VTK applications may also be written using these interpreted programming languages.