-   Program must result in a Ray Tracer.
-   The Program is programmed in c++.
-   In the Ray Tracer, there are objects: 3 Spheres and 1 Floor.
-   The Floor is made out of black and white squares, like a chessboard.
-   The Program contains the methods laid out in all previous assignments.

Tests are done visually. The result of the program must look like the example
provided in the assignment: 
http://wiztech.nl/module_c++_voor_industriele_toepassingen/les_5_templates/overig_lesmateriaal/eindopdracht/ray_tracer/eindopdracht.pdf
There are 4 Objects visible: 3 Spheres and 1 Floor.
The Spheres reflect other Spheres and the Floor.
The Floor is like a chessboard.

Space
This raytracer gives an image of a 3D space. You'll be able to see what is close and what is far.
We work with 3 axis: x, y and z. The x-axis is the horizontal axis. The y-axis is the vertical axis.
The z-axis is the axis that is rightly angeled on the other axes. It determines how far an Object is.
The coördinate: (0, 0, 0) is in the center of the screen, on the screen.
x=1 is one meter to the right. y=1 is one meter up. And z=1 is one meter behind the screen. 
The class RayScanner calculates the x and y of the screen, based on the dimensions of my screen.

There is a class Vec3D.
It has methods to perform calulations on the 3D Vectors, like add. 
Which methods are implemented by this class is determined by the assignment.

There is a class Ray.
It has the methods provided in the assignment.
A Ray has two Vec3Ds, a support and a direction vector. With Rays, 
we can check whether there is a object in the way of the camera.
Rays start in the camera, and go through the screen. If they hit a Object,
the program displays a char on the place of the screen.
This way an image becomes visible.

There is a class Sphere.
It has the methods provided in the assignment: bool Sphere::hit(Ray const &ray) const;
Sphere is a typ of Object, and therefore a child-class.
A Shpere is a object in 3 dimensions. It has a center, which is stored as a Vec3D
and a radius.

There is a class Floor.
It has the methods provided in the assignment: bool Floor::hit(Ray const &ray) const;
The Floor is a typ of Object, and therefore a child-class.
The Floor is a object in 3 dimensions. It is a surface behind the screen.

There is a class Object.
The classes Sphere and Floor are childs of this class.
Object has a virtual method: virtual bool hit (Ray const &ray) const = 0;
With this method, we can loop through Spheres and Floors, which are both Objects, and call the hit method in one line.

There is a class RayScanner.
It has 4 objects with which the image is to be constructed.
The main function creates the Objects in a vector<Object*>.
An instance of RayScanner is than defined.
RayScanner has a scan() method. This method constructs the image by doing this basic process:
-   Take the width and height of the screen. Calculate how many pixels/chars are needed.
-   For each pixel/char, construct a Ray that goes from the camera through the screen on the place of the pixel.
-   Go through all Objects: check whether the Ray hits any Object.
-   Whether it hits determines what char is printed.