An Effective way to explain Ray Tracing? In my CS class in high school I'm doing a presentation on Computer Graphics and I wanted to talk about Ray Tracing. I was wondering what would be the easiest way to do this without confusing my audience?

What are some of your personal favorite analogies and explanations that have worked effectively to people who have never touched the field?

Please don't mistake this as a 'do my homework' type question. I'm just curious to see what has worked and what hasn't.
Here's my introduction: http://www.gabrielgambetta.com/computer-graphics-from-scratch/raytracing.html It uses the somewhat contrived analogy of making a painting by putting a grid in front of a real landscape, and painting a square of the colour you see through each hole in the grid. A raytracer is essentially that, but with some linear algebra :)