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 that VTK applications may also be written using these interpreted programming languages. Some optional additional packages, if detected during configuration, are used in preference to versions provided in the source code. These packages, available from SlackBuilds.org, are: jsoncpp proj You can enable a number of optional features by passing variables to the script (VAR=yes|no ./VTK.SlackBuild): IMAGING=yes|no (default: yes) MPI=yes|no (default: no), requires openmpi TK=yes|no (default: yes) VIEWS=yes|no (default: yes) WEB=yes|no (default: no), requires python3-twisted JAVA=yes|no (default: no), requires jdk PYTHON=yes|no (default: yes) QT=yes|no (default: yes) NB. Some combinations of options are known to result in compilation errors if the build machine already has VTK installed. Please remove any VTK installation before running the SlackBuild.