This example shows one way to get a HUD (Heads-Up Display) in a 3D graphical simulation. Most often, text is one of the elements needed for a HUD, and text support is lacking in all flavors of OpenGL, including WebGL. Text is easy when drawing on a 2D canvas, however. So one way to solve this problem is to overlay the canvas used for 3D graphics with a second canvas to be used for 2D graphics. This is the approach taken in this application.