TP2 is a free tool similar to TECPLOT, but can plot many more types of files. TP2 recognizes 28 different 2D, 3D, and even 4D files and comes with lots of examples, including topography, velocity vectors, a klein bottle, and Yoda's head, which you can rotate using the directional keys on the number pad. TP2 can also read simple FORTRAN and C code and apply this to data. There are also a few examples showing how to define 3D shapes using code that is interpreted on the fly. This first figure shows how several types of surfaces can be displayed:


This next figure shows a variety of different file types and what they look like in TP2:


The latest version can be downloaded from the free software page  .