Back in the mid eighties rendering very simple three dimensional scenes using ray tracing took a great deal of time.

"...images generated using some of the above improvements to ray tracing. They all took approximately 50 minutes each to compute on a VAX 780." - From http://www.cs.yorku.ca/~amana/research/cones.pdf

Example image found here: http://www.cs.yorku.ca/~amana/research/images/spheres.jpg

A DEC VAX 780 cost over a hundred thousand dollars - http://www.computerhistory.org/revolution/mainframe-computer...