When marriage is Outlawed, 
Only Outlaws will have Inlaws.

Concept 4.1 : Specifying a Shading Model
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Idea:
=====
To your left is rendered a triangle.  This
triangle has been rendered with GL_SMOOTH as
the Shade model.  Click on the display with the right 
mouse button and hold it down.  The pop up menu allows 
you to toggle between Smooth and Flat shading.  

A line or a filled polygon primitive can be drawn
with a single color(flat shading) or filled with
many different colors (smooth shading also called
Gouraud shading).  You specify the desired shading
technique with glShadeModel()

With flat shading, the color of one particular vertex
of an independent primitive is duplicated across all
the primitives vertices to render that primitive.  With
smooth shading, the color at each vertex is treated
individually.  For a polygon primitive such as our 
triangle, the colors for the interior of the polygon are
interpolated between the vertex colors.  With smooth
shading neighbouring pixels have slightly different color 
values.  For the flat shading model , in the case of our
polygon we see it as blue because the last vertex of
the triangle is specified with the color blue.