For example, consider if someone wanted to draw a pie graph on some terrain. But the graph lays on top of the terrain. In my case, I just want to draw a circle on top of a Cube.
I suppose I could draw a 3D disc if I had to. Any thoughts?
You could use a projector placed above the cube or you could manually place a plane with the pie graph texture on it directly above the cube.
However, if all you wanted to do was simply draw a solid circle of one color, you could create a cylinder gameObject, set the Y scale to something like .01, place that cylinder above your cube, set the material's color to whatever color you need, and scale that using Vector3.Scale.