Attached Link: http://www.phase2.net/claygraphics/Marbles.html

TIR is for stuff like diamonds, gems and such, also anything made with a glass or transparent material added to it, on stuff like cut jewels, it gives it that gleam like when you look at a diamond or ruby in a jewelry shop, that sparkle is caused by internal reflections.Also on your depth of field, might as well crank the rays up high if it's a fairly complex scene, will take longer but the results are worth it:-) here is a url to a Depth of Field Done at full premium rendering, done on a network rnder between two machines, took about 14 minutes: http://www.phase2.net/claygraphics/Marbles.html

Do atleast one thing a day that scares the hell outta ya!!