I like the walls made of spheres! The real Cornell box is about 2 feet cubed IIRC... that would make the units of this scene file something close to centimeters... which would mean the walls are spheres with a diameter of about 1.2 miles.

Last time I saw the box in person, I made sure to leave some fingerprints. :P

> Realistic Ray Tracing, by Peter Shirley > Almost 100% of smallpt is derived from this book.

FWIW, Peter Shirley distilled all the fun parts of Realistic Ray Tracing into an easy quick e-book available for $3, or free with the trial. "Ray Tracing in One Weekend."

https://www.amazon.com/gp/product/B01B5AODD8/

Blog post about it w/ more code & lots of resources: http://in1weekend.blogspot.com/2016/01/ray-tracing-in-one-we...