I don't think it's a waste of time. Ray tracing puts you on the path to real-time global illumination, which I think everyone is going to want if it's in reach. It also makes a lot of non-graphics tasks easier, like determining line-of-sight visibility between arbitrary points in the scene or doing collision detection.

Besides, computational power isn't something we necessarily need to conserve for its own sake. We stopped using Gourad shading when the hardware became fast enough that we didn't need it anymore. Polygon rasterization will stick around for a long time I think, but I don't think it will always be an essential part of everyone's real-time rendering technology stack.

http://www.paulgraham.com/hundred.html

> I can already tell you what's going to happen to all those extra cycles that faster hardware is going to give us in the next hundred years. They're nearly all going to be wasted.

> I learned to program when computer power was scarce. I can remember taking all the spaces out of my Basic programs so they would fit into the memory of a 4K TRS-80. The thought of all this stupendously inefficient software burning up cycles doing the same thing over and over seems kind of gross to me. But I think my intuitions here are wrong. I'm like someone who grew up poor, and can't bear to spend money even for something important, like going to the doctor.