Computer Science 102
                               Quiz 6      Name ______________________

1. Suppose a plane in 3 dimensional space has normal vector N and the
   P and Q are two different points that both lie in the plane.  Which
   of the following will always have the value 0.

   a.  N dot P                     b. P dot (N - Q)

   c.  P dot Q - N                 d. N dot (P - Q)

2. Suppose a ray is fired from viewpoint V with unit direction vector D.
   The ray is parallel to the plane if:

   a. V dot D = 0                  b. V dot N = 0


   c. D dot N = 0                  d. (N - D) dot V = 0

3. Suppose ray hits the plane at a distance t from V. The
   coordinates of the hitpoint are:

   a. P + tN                       b. V + tP

   c. D + tV                       d. V + tD


 4. Suppose a plane is defined by N = (0, 0, 1) and Q = (0, 0, -5)
    where N is the normal and Q is a point on the plane. Suppose
    V = (4, 3, 2) and D = (0, 0, -1)

    a. The distance from V to the Hitpoint?






    b. Give the coordinates of the Hitpoint






    Hint: Although it is possible to solve this using the plug and pray
    method with formulas presented in class, this approach will take
    excessive time and is likely to produce arithmetic errors.  The correct
    approach is to visualize the geometry of the problem in your head
    (or on paper).  If you do that correctly,  the solution can be
    readily computed in your head with resorting to any dot products.