Sex is not the answer.  Sex is the question.
"Yes" is the answer - Swami 'X'

Concept8 : Absolute or Relative Units ?
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Idea:
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The question left unanswered is what kind of 
measuring units does OpenGL use to draw objects.
Is it cm, meter, inch?. Do you know the answer?.
The gluOrtho2D(left, right, bottom, top); function:
This defines a clipping rectangle with the lower 
left corner at (left, bottom) and the upper-right corner at
(right, top).  In our case gluOrtho2D(0.0, 1.0, 0.0, 1.0)
specifies a viewing rectangle which is 1 unit long and
1 unit wide.

Experiment:
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Change the values for right, and top to '2'.  Our 
triangle becomes half the original size!

So what do you think is the answer?.  
The answer is that it is relative to the size of
the viewing volume.