MayaVi

MayaVi is a free, easy to use scientific data visualizer. It is written in Python and uses the amazing Visualization Toolkit (VTK) for the graphics. It provides a GUI written using Tkinter.

Features
- An easy to use GUI.
- Can be imported as a Python module from other Python programs and can also be scripted from the Python interpreter. 
- Visualize computational grids.
- Visualize scalar, vector and tensor data.
- Quite a few data filters are also provided.
- Supports volume visualization of data via texture and ray cast mappers.
- Support for any VTK dataset using the VTK data format. Works for rectilinear, structured, unstructured grid data and also for polygonal data. Both the original VTK data formats and the new XML formats are supported.
- Support for PLOT3D data. Only the binary structured grid format works because of current limitations in VTK's vtkPLOT3DReader. Simple support for multi-block data is also incorporated.
- Support for EnSight data. EnSight6 and EnSightGold formats are supported. Only single parts are supported at this time.
- Multiple datasets can be used simultaneously. Multiple modules can be viewed simultaneously.
- Support for data files belonging to a time series.
- A pipeline browser with which you can browse and edit objects in the VTK pipeline. A segmented pipeline browser is used to make it easier to look at parts of the VTK pipeline.
- Support for importing a simple VRML or 3D Studio scene. Texturing in VRML is not yet supported due to limitations in VTK's vtkVRMLImporter.
- A modular design so you can add your own modules and filters.
- A Lookup Table editor to customize your lookup tables easily while visualizing data!
- An interactive data picker that lets you probe your data interactively.
- A light manipulation kit that lets you modify the lighting of the visualization.
- The visualization (or a part of it) can be saved and reused in the future.
- Export the visualized scene to a Post Script file, PPM/BMP/TIFF/JPEG/PNG image, Open Inventor, Geomview OOGL, VRML files, Wavefront OBJ or RenderMan RIB files. It is also possible to save the scene to a vector graphic via GL2PS. This is only available if VTK is built with GL2PS support.