In pg's ANSI Common Lisp, he defines a ray tracer in one page of code, creates all the necessary functions for spheres in another page, then inserts 28 spheres

In pg's ANSI Common Lisp, he defines a ray tracer in one page of code, creates all the necessary functions for spheres in another page, then inserts 28 spheres and prints out the world in a dozen lines of code. There's part of a page of utility functions, like creating a point structure. You can examine the code here: http://lib.store.yahoo.net/lib/paulgraham/acl2.lisp http://lib.store.yahoo.net/lib/paulgraham/acl2.lisp . Search for the first instance of "surface".