Computer Science 102
                                  Short Program 5
                               Due 29 March 11:59PM

For this program the ONLY authorized source of assistance is
Dr. Westall or the TA's. ANY OTHER DISCUSSION of the program no matter how "high
level" or "peripheral" (e.g. Have you started/finished it yet?)
is STRICTLY FORBIDDEN.  Any student who observes improper behavior
is encouraged to report it to Dr. Westall. Reports that can be
verified will be rewarded with a 20 point bonus on the assignment for
the student doing the reporting and an F for the course for the
student being reported!!

Adhere to the following programming standards.  Violations will
lead to deductions.

(1) no function should be longer than 30 lines code + whitespace.
(2) the maximum nesting level in any function is ONE
(3) code lines should not extend beyond column 72
(4) no more that one statement may be written on a single line
(5) use reasonably descriptive names for variables and functions
(6) package all functions into a single source code module named camera.c
(7) your program should compile without any warnings with gcc -Wall
(8) indenting should be consistent with logical nesting
(9) diagnostic / debug prints should be disabled/deleted in
    your submission.

In this assignment you will implement diffuse illumination in your
C++ raytracer.  Use the following class definition.

class light_t
{

public:
   light_t(){};
   light_t(FILE *in, model_t *model, int attrmax);

   virtual ~light_t(){};

   virtual void    illuminate(model_t *, object_t *, drgb_t *);
   inline  void    light_item_dump(FILE *);

protected:
   vec_t   location;
   drgb_t  emissivity;
   char    name[NAME_LEN];

private:
   int     cookie;
};

I recommend that you follow the procedures in the notes for doing this
VERY CAREFULLY.  If you don't read and follow the notes you will become
massively confused and an ugly mess will result.

Here is the order in which I recommend that you complete the various
tasks that are necessary:

1 - Add the light_t class to ray.h
2 - Modify the model.cpp function so that its parser recognizes the
    light entity and creates a new light_t class.
3 - Modify the dump() method of the model_t class to invoke the light_dump()
    function.
4 - Write the light_t constructor
       light_t(FILE *in, model_t *model, int attrmax);
    which parses the attributes and puts the new light_t structure
    on the end of the light list.
5 - Write the light_dump() C function which processes the light list
    and invokes light_item_dump() for each light. Add its prototype
    to rayhdrs.h
6 - Write light_item_dump()
7 - STOP WRITING AND TEST THIS MUCH.  DON"T WRITE ANOTHER LINE UNTIL
    THIS MUCH WORKS.
-----------------------------------------------------------------------
8 - Modify the raytrace.c module adding in the add_diffuse() function
    given in the notes.
9 - Make the additional mods suggested in the notes to cause raytrace()
    to call add_diffuse
10 - Write the illuminate method of the light_t class.

----------------------------------------------------------------------

It is very likely you will need to have optional debug code that will
allow you to print:

   the vector from the hitpoint to the light
   the cosine of the angle
   the distance from the hitpoint to the light
   the diffuse reflectivity of the material
   the final diffuse illumination
   occlusion data such as:

#ifdef DBG_OCCLUDE

      fprintf(stderr, "%-10s occ by %-10s at (%4.1lf, %4.1lf, %4.1lf) (%4.1lf, %4.1lf, %4.1lf)",
                   light->name, obj->objname,
                   hitobj->hitloc.x, hitobj->hitloc.y, hitobj->hitloc.z,
                   obj->hitloc.x, obj->hitloc.y, obj->hitloc.z);

#endif