Real Time Relativity
  Real Time Relativity is a computer program that allows the user to fly through a virtual world governed by relativistic physics. The user controls a 'rocket' carrying a 'camera'. The rocket may be accelerated and steered, and the camera may be pointed in any direction. It takes advantage of the fact that video cards provide inexpensive data-parallel processing and are designed to perform rapid arithmetic on four-dimensional vectors. 
C. M. Savage, A. C. Searle, L. McCalman