Each line of the file may contain a single keyword followed by some
values.  Top-level keywords include GLOBAL_AMBIENT, GLOBAL_ATTENUATION, 
SPHERE, BOX, and POINT_LIGHT.  

The lines following a top-level keyword provide values for properties
of the specified top-level item.  A blank line separates a property
list from the subsequent top-level item. The general format is:

A file may contain any number of top-level items (except for
GLOBAL_AMBIENT and GLOBAL_ATTENUATION, each of which should only occur
once) and they may appear in any order in the file.

All positions are in eye coordinates.  Like in OpenGL, the eye is assumed
to be at (0,0,0), looking in the negative  z direction.  ``Up'' is along
positive y. ``Right'' is along positive x.

For SPHEREs and BOXes, the (x,y,z) position specifies the location of the 
center of the object.  For BOXes, ORIENTATION specifies a rotation matrix
describing the orientation of the BOX with respect to the eye coordinate
system (This should be fairly easy to extract from your Homework 3 code).

The format is:

GLOBAL_AMBIENT r g b
GLOBAL_ATTENUATION kc kl kq

SPHERE 
RADIUS radius 
POSITION x y z
DIFFUSE r g b
SPECULAR r g b shininess
TRANSPARENCY fraction
REFRACTION_INDEX fraction

BOX
SIZE x y z
POSITION x y z
ORIENTATION m11 m12 m13 m21 m22 m23 m31 m32 m33
DIFFUSE r g b
SPECULAR r g b shininess
TRANSPARENCY fraction
REFRACTION_INDEX fraction

POINT_LIGHT
POSITION x y z
DIFFUSE r g b
SPECULAR r g b