How to do it...

To create elements in a scene using 3D primitives, follow these steps:

1. Create a new 3D project.
2. Import the beware.png image (or your own) into the newly created 3D project.
3. Add a 3D Cube to the scene by going to GameObject | 3D Object | Cube. In the Hierarchy window, rename this Cube-signpost.
4. Set Position of the Cube-signpost GameObject to (0,0,0) and its Scale to (2, 1, 0.1) by selecting it in the Hierarchy window and then setting these coordinates in the Inspector window. This should make it a portrait-style rectangle shape that only has a little depth (like a big, flat piece of wood for a signpost...):

5. Create a 3D plane named Plane-sign by going to GameObject | 3D Object | Plane. Then, in the Hierarchy window, make it a child of Cube-signpost (that is, drag Plane-sign onto Cube-signpost). This means its properties will be...