Quote - To quickly illustrate 'perpendicular', take a pen and place one end on a table so that the pen is standing up.  The table surface is the polygon.  The long dimension of the pen is perpendicular to the table's surface and could be used to represent the table surface's normal. :)

 

or...just drink beer and fall on the floor, look at the wall in front of you...it is perpendicular to you body. lol!

bookmark that! :biggrin:

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