be read by the program getinfo.

2.  Scene Description

     A scene description file represents a three-dimensional
physical  environment in Cartesian (rectilinear) world coor-
dinates.  It is stored as ascii  text,  with  the  following
basic format:

        # comment

        modifier type identifier
        n S1 S2 S3 ... Sn
        0
        m R1 R2 R3 ... Rm

        ! command

         ...


     A comment line begins with a pound sign, `#'.

     The scene description primitives all have the same gen-
eral  format,  and  can  be either surfaces or modifiers.  A
primitive has a modifier, a  type,  and  an  identifier.   A
modifier  is  either  the identifier of a previously defined
primitive, or void.  An identifier can be  any  string  (ie.
sequence of non-blank characters).  The arguments associated
with a primitive can be strings or real numbers.  The  first
integer  following  the  identifier  is the number of string
arguments, and it is followed by the  arguments  themselves.
The  next integer is the number of integer arguments, and is
followed by the integer arguments.  (There are currently  no
primitives  that use them, however.) The next integer is the
real argument count, and it is followed by  the  real  argu-
ments.

     A line beginning with an  exclamation  point,  `!',  is
interpreted  as a command.  It is executed by the shell, and
its output is read as input to  the  program.   The  command
must  not  try to read from its standard input, or confusion
will result.

     Blank space is generally ignored, except as  a  separa-
tor.  The exception is the newline character after a command
or comment.  Commands, comments and primitives may appear in
any combination, so long as they are not intermingled.

2.1.  Primitive Types

     Primitives can be surfaces, materials, textures or pat-
terns.   Materials  modify  surfaces,  textures and patterns
modify textures, patterns and materials.

2.1.1.  Surfaces

     A scene description will consist  mostly  of  surfaces.
The basic types are given below.








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