Is there a convenient way to make a rainbow material that varies smoothly along a torus? In the image below, I made a new emission material for each of the 32 segments along the major axis, changing the HSV hue by 1/32 each time. Clearly, you can still see bands of color; plus, it's labor intensive to make all of these materials, and challenging to edit afterwards.
Ultimately, I'd like to have the material's color spin around the object.