Conscience is what hurts when everything else
feels good

Concept 3.3: Fog - A simple example
===================================

Idea:
=====
We render five spheres along the -Z axis.  These
are progressively obscured by fog/

Experiment:
===========
The options allow you to change the fog mode, the
density, the start and finish points for the fog.

GL_FOG_MODE : is a single integer or floating
point value that specifies the equation to 
be used to compute the fog blend factor, f.
Three symbolic constants are accepted: GL_LINEAR,
GL_EXP and GL_EXP2.  

GL_FOG_DENSITY : is a single 
integer or a floating-point value that 
specifies density; i.e. the density used in
both the GL_EXP and GL_EXP2 equations.  
Notice that GL_FOG_DENSITY should have
no effect on GL_LINEAR type of fog situations.

GL_FOG_START : is a single integer or 
floating point value that specifies start, the
near distance used in the linear fog equation.
The default near distance is 1.0.  Again this
does not have an effect on GL_EXP and GL_EXP2
equations.

GL_FOG_END : is a single integer or floating
point value that specifies end, the far distance 
used in the linear fog equation.  The default
far distance is 1.0.  Again this affects only
the GL_LINEAR fog equation.

GL_FOG_COLOR : contains four integer or floating
point values that specify the fog color.  In our
example here we use a constant fog color of grey
because that is a realistic color for fog occuring
in nature.