Shadow Casting Sketch Dump

I've been learning technical shadow casting in 1, 2, and 3-point perspective. This partly grew out of a need to be able to teach it to my students, and partly for personal creative reasons. Around 15 years ago in undergrad I learned this material on a very basic level, but was left with more questions than answers. Out of frustration I started just kind of making it up when I needed to draw cast shadows in a scene. It's always been a little frustrating, and I would usually erase and redraw several times before arriving at something that worked. So I want to be able to provide a thorough knowledge of this material to my students, and for myself.

Here is a selection of the fruit of this research (which is still underway):

Shadow casting using a "local" light source (man made light source). Also called a "Point Source":

Here is a diagram I made in Adobe Illustrator for Shadow casting in 1 and 2-point perspective using a "natural" light source (sun light) and several drawings using this method:


Side lighting scenario. I don't have a diagram for how this works, but this can be found in most perspective books.
After I figured out shadow casting in 1 and 2-point perspective I discovered something interesting... shadow casting in 3-point perspective is conspicuously missing from all 15 perspective drawing books that I have on my shelf (and several PDF books that I have on my hard drive), and I couldn't find even a mention of it on the web. The standard methods just didn't work in 3-point when I tried them on my drafting table, so I experimented until I came up with a method that has a converging "Solar Line". I've tested this so many times now that it's insane, and it works every time.