vtk

VTK, or the Visualization Toolkit, is an open-source software system for 3D computer graphics, image processing, and visualization. It provides a large, modular library of data processing and rendering components that can be used to build custom visualization applications. The project is cross-platform and available under a BSD‑like license, with bindings for C++, Python, Java, and Tcl.

At its core, VTK uses a pipeline architecture in which data objects are produced by sources, processed by filters, and finally rendered by mappers and actors in a scene. The data model includes common data structures such as vtkImageData, vtkPolyData, and vtkUnstructuredGrid, all derived from a common vtkDataObject. Algorithms are implemented as vtkAlgorithm objects and connected into pipelines using information objects.

Rendering in VTK relies on a scene graph that is managed by renderers, render windows, and interactor styles. Key components include vtkRenderer, vtkRenderWindow, and vtkRenderWindowInteractor, along with mappers, actors, and lighting. The library supports volume rendering, isosurface extraction, contouring, glyphing, and extensive shading and post-processing capabilities. Higher-level applications, such as ParaView and 3D Slicer, are built on top of VTK and rely on its data model and rendering pipeline.

VTK is written in C++ with language bindings for Python, Java, and Tcl, enabling use from scripting as well as compiled languages. It is widely used in scientific visualization, medical imaging, computational fluid dynamics, and related fields, and remains a core component of major visualization platforms.