Raymarching is one of those techniques that has extreme simplicity and yet can generate very complex scenes from an essentially mathematical description; I think it's one of the best examples of an elegant algorithm.

More info here:

http://iquilezles.org/www/material/nvscene2008/rwwtt.pdf

http://www.iquilezles.org/www/articles/distfunctions/distfun...

Nice! Reminds me of The Business Card Raytracer[0].

[0]http://www.cs.utah.edu/~aek/code/card.cpp

Also the 1bir (1 Block Interactive Raycaster), a raycaster for Commodore 64 in 254 bytes (source code included):

http://www.pouet.net/prod.php?which=61298

Disclaimer: I am the author of 1bir.

And the dissection: http://fabiensanglard.net/rayTracing_back_of_business_card/