Computer Science 102
                                  Quiz 2              Name____________________

1. In the ray tracing model that we will use:

   a. the viewpoint lies in +z space and  b. the viewpoint lies in -x space and
      the scene lies  in -z space            the scene lies  in +x space

   c. the viewpoint lies in -z space and  d. the viewpoint lies in +x space and
      the scene lies  in +z space            the scene lies  in -x space


2. A unit vector from the viewpoint toward a pixel on the "screen" always has:

   a. a negative x component              b. a negative y component

   c. a negative z component              d. negative x, y, AND z components


3. Suppose world coordinate dimensions are 8 units wide by 6 units high
   and the viewpoint is at (4, 3, 6).  A unit vector from the viewpoint
   toward the pixel at the top left corner of the screen has:

   a. negative x, y, and z components     b. negative y and z but positive x

   c. negative x and y but positive z     d. negative x and z but positive y


4. The function that was suggested last time for mapping pixel to
   world coordinates was:

    a. world_x = world_size_x * win_x  /  (win_size_x - 1)

    b. world_x = world_size_x * (win_size_x - 1) / win_x

    c. world_x = world_size_x * win_x  *  (win_size_x - 1)

    d. world_x = win_size_x * win_x  /  (world_size_x - 1)

5.  Suppose the viewpoint is at location V and the world coordinates of the
    point on the screen through which a ray passes is W.  A vector in
    the direction the ray is fired is given by:

    a. V + W                              b. V - W

    c. W - V                              c. (V + W) / 2.0