Guest on HdrLabs by Bob Groothuis who posts about creating a 1 meter square real live reference cube by way of rapid prototyping the connectors needed for the collapsable structure… pretty cool stuff! Check out the Rapid Prototyping A 3D reference Cube article here.
“A 3D Reference Cube is a device that assists in 3D tracking and measuring. If you photograph it along with your background plate, you’ll have the perfect placeholder for your CG objects.”