I've been watching "Warcraft 3", and suddenly realized that I have no idea how to draw a circle on a surface.
Here is an example:
I guess this is projection? I also have very little idea of how to draw a shadow. I only somewhat know OpenGL.
It is also interesting how this circle seems to not perfectly repeat the shape of that cliff. My guess is that it's drawn using a height map, which is stored somewhere separately, and not as the cliff, itself. It looks like it actually goes underwater, but it may be just a compression artifact.