If you were wondering why Baymax in Big Hero 6 looked so good (or you just want a primer in CG rendering), check this 10-min film from Walt Disney Animation Studios explaining how path tracing works and how their Hyperion renderer makes it possible to, for example, render vast city scenes with out the use of matte painting extensions.

Read more about Hyperion here.

And if you really need to go deeper, read about the difference between path tracing and ray tracing here.

The Hyperion development team: Andrew Fisher, Patrick Kelly, David Adler, Dan Teece, Christian Eisenacher, Doug Lesan, Greg Nichols, Chuck Tappan, Brent Burley, Sean Jenkins, Andy Selle, Noah Kagan, Lisa Young, Matt Chiang, Ralf Habel, Darren Robinson, Peter Kutz