The Visualization ToolKit (VTK) is an open source, freely available software system for 3D computer graphics, image processing, and visualization used by thousands of researchers and developers around the world.
Developed by the Lawrence Livermore National Laboratory, VisIt contains a rich set of visualization methods—such as contour plots, pseudocolor plots, volume plots, vector plots, and boundary plots—for visualizing scientific data. VisIt allows the ability to provide quantitative as well as qualitative information from a scientific data set.