In a previous life, I rendered bottles for a living, and as I was doing it without rendering software, I was always happy when the assignment called for glass and bummed when it called for PET. PET bottles always had crazier shapes, and the amount of reflectivity required to get the material to read was a PITA.
I thought of this while watching illustrator Marcello Barenghi's YouTube channel, specifically this illustration of a Heinz ketchup bottle, which clearly reads as PET:
Obviously a hyperreal illustration and an ID rendering are two different things, as the latter's more concerned with form, gesture and emotion than cold accuracy, but Barenghi's understanding of light, texture and surfaces is unparalleled. So much so that while his channel is called "How to Draw," it might as well be called "Things Most of Us Wouldn't Want to Render by Hand." Like this ruby:
Or this Brazuca:
For those of you students looking to pick up some old-fashioned hand rendering skills, or just seeking to see how Barenghi deals with light and reflectivity with different materials, the man has posted literally hundreds of videos (his channel's got 38 million views to date!). Here's a quick sampling:
Check 'em all out here.