Questions about drawing simple objects.

For the purpose of debugging it is often useful to have some simple way of drawing cubes, squares, grids and lines in the gameworld. Say, a world grid for building placement or two 3D cubes connected by lines or hash marks to illustrate a dynamic pathfinding vector.

I realize the mission editor has all this capability already in one form or another, but trying to locate how they did it in code has been difficult. I almost wonder if I won't have to implement a new object type in code like the fxRender Object. I'm just hoping I missed the boat and there is a nice method for doing what I want.

Does anyone know of a simple resource for drawing simple shapes in the game world? Or perhaps they could direct me in the right direction? This is entirely for debugging so it doesn't need to be robust enough for a multiplayer environment. Thank you in advance for any help with this!