Compleat Angler (1979)
First Ray tracing, first CGI reflections
1) After receiving his PhD from NCSU in 1978, Turner Whitted left for Bell Labs and proceeded to shake the CGI world with an algorithm that could ray-trace a scene in a reasonable amount of time. His film, The Compleat Angler is one of the most mimicked pieces of CGI work ever, as every student that enters the discipline tries to generate a bouncing ray-traced ball sequence.
2) Ray tracing is a rendering technique for generating an image by tracing the path of light as pixels in an image plane and simulating the effects of its encounters with virtual objects. The technique is capable of producing a very high degree of visual realism, usually higher than that of typical scanline rendering methods, but at a greater computational cost. This makes ray tracing best suited for applications where the image can be rendered slowly ahead of time, such as in still images and film and television visual effects, and more poorly suited for real-time applications like video games where speed is critical.
3) On this link from Pixar behind the scenes you can see a lot better quality version of this film (small part of it).
4) Real-time ray tracin (in video games) is incredible hard to made. First attempt to do video game with ray tracing was Quake 3: Ray Traced (2004). Ray tracing technology is only starting to appear widely in a videogames from 2017-18.