I tried to make this work through the UI system at first, and almost got there too, but it was a square instead of a circle. To make it a circle, first I tried using a custom shader with a mask texture, and I couldn’t get that to work. Then I tried putting the map texture on a mesh and rendering that to a texture and showing that in the UI, I couldn’t get that to work either. So this is a mesh that’s attached to the camera in world space.
One cool thing about this solution is that I can make the minimap receive in-game lighting. Maybe I’ll add a decorative rim or something to it and add lighting to that without adding lighting to the map texture. Maybe put the “N” (for north) on the decorative model instead of in the generated texture like it is now.