>I make an educated guess saying that a simple limited 3d
>one-line led based propeller display could easily be modified
>to use this 3d principle, by simply placing the line of leds
>at an angle (think line diagonal in a cylinder). This
>should be able to display any biconical shape.

I would have thought that the way to do it with a propeller clock type 
emitter would be to have a head sensing trick like the guy that uses a Wii 
handheld sensor strapped to his head for sensing to rotate the image on a TV 
screen. 

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