Well, not exactly Atomic Age, which I think of as late 40’s through mid 60’s, but close – what would you call it when you’re rendering on a plotter and drawing “+” signs for shading?

Arthur Appel’s paper from 1968 is considered the first use of ray casting for rendering, for eye rays and shadow rays.

One surprising part is that the paper includes the idea of shooting rays from the light and depositing the results on the surfaces – early photon mapping, or radiance caching, or something (details aren’t clear).

Update: an anonymous source let me know, “When I worked briefly at the IBM TJ Watson lab, I made a point of seeking out Art Appel. He was friendly and nice. As I recall, he said that he was working as technical support at the time of the ray tracing work. As he described it, most of his day was spent hanging around, waiting to answer the phone and help people with computer issues (this may have been a self-effacing description of a very different or important job, for all I know). He said that he had lots of free time during the day, and he was interested in using the computer to make images, so his ray tracing work was basically a hobby!”