ECSE-4750 Computer Graphics, Rensselaer Polytechnic Institute, Midterm Exam, Fall 2013, 10 Oct 2012 4-5:30

NAME: ____________________________________ EMAIL:___________________________ RIN:______________

There are 5 pages with 20 questions, each worth 2 points. Answer every question but 2. You may write FREE as the answer for two questions (and get the 2 points each).

Please sit in alternate seats, counting in from, and starting next to, the outside walls.

This exam is closed book: you may use calculators and one 2-sided letter-size note sheet that you brought with you. You may not use computers or communication devices, or share material with other students.

1. _____/(2 points) What display technology depends on the ability of an electric field to straighten out a corkscrew molecule?
   
   
   
   
   
   
   
   
   
2. ________/2 Why can the following not possibly be a 3D Cartesian rotation matrix?
   {$ \begin{pmatrix} 1& 0 &0\\1 & 0 &0\\0& 0 &1\end{pmatrix} $}
   
   
   
   
   
   
   
   
3. ________/2 If a=(1,2,3) then write {$(a\cdot p)\, a$} as a matrix M, depending only on {$a$}, times {$p$}.
   
   
   
   
   
   
   
   
   
   
   
   
   
4. ______/2 Can the volume of a small cube change when its vertices are rotated? (yes or no). Why (not)?
   
   
   
   
   
   
   
   
   
5. _____/2 What does this do:
   glutDisplayFunc(display)
   
   
   
   
   
   
   
   
   
6. _____/2 One problem with putting all your vertices into an array is that each vertex might be a member of a variable containing other info, such as this:

     Class Vert {
     public:
     float coords[3];
     float color[4];
     float normal[3];
     }
     Vert verts[10];
   
   

   Therefore the coordinates of successive vertices are not adjacent. How can you tell OpenGL about that when using a vertex array? You don't need to give the precise syntax in you can describe the idea or give the key word describing this.
   
   
   
   
   
   
   
   
   
7. _____/2 What does glFlush do?
   
   
   
   
   
   
   
   
8. _____/2 Use the vector formulation or your intuition to rotate the point (0,2,2) by 60 degrees about the axis (0,1,1).
   
   
   
   
   
   
   
   
   
9. ____/2 What's the dot product of these 2 vectors: (1,2,3), (4,5,6)?
   
   
   
   
   
   
   
   
   
10. ____/2 When are glPushMatrix() and glPopMatrix() useful?
    
    
    
    
    
    
    
    
    
11. ____/2 What feature in OpenGL is used to display the closest object when several objects overlap the same pixel?
    
    
    
    
    
    
    
12. ____/2 Consider this sequence of calls:

      glColor3f(1.,1.,1.);
      glColor3f(0.,1.,0.);\
      glVertex3f(1.,1.,1.);
      glVertex3f(2.,2.,2.);
    
    

    1. What color is the vertex (1,1,1)?
    2. What color is the vertex (2,2,2)?
    
    
    
    
    
    
    
    
    
13. ____/2 Why do we like to group different physical input devices into the same logical input device?
    
    
    
    
    
    
    
    
14. ____/2 Here's how picking might have been implemented: When you pick an object, the line number of the glBegin call to draw the closest object covering that pixel might be returned by the pick routine.
    Why would this idea be inadequate?
    
    
    
    
    
    
    
    
    
15. _____/2 What's the quaternion representing a rotation of 180 degrees about the axis (1,0,0)?
    
    
    
    
    
    
    
    
    
16. _____/2 What 3 simpler operations would you combine to rotate an object by 90 degrees around the point (1,2,3) about the axis (1,0,0)? That is, the axis does not go through the origin, but goes through the point (1,2,3).
    
    
    
    
    
    
    
    
17. _____/2 When rendering a triangle, you are given various properties at each vertex, and then need to interpolate them at each pixel inside the triangle. One such property is position. Name two other properties.
    
    
    
    
    
    
    
    
    
18. _____/2 Here is a 3D homogeneous point: (1,2,3,4). What Cartesian point does it correspond to?
    
    
    
    
    
    
    
    
    
19. _____/2 Give the 4x4 homogeneous matrix for a rotation by 90 degrees about the Z axis.
    
    
    
    
    
    
    
    
    
20. _____/2 Suppose that you're writing a spacewar game, where there are 10000 asteroids that your spacecraft might hit. (To make this question simple) The asteroids are not moving. Repeatedly testing for a collision between your spacecraft and each asteroid is too slow. How can you make this faster (w/o using faster hardware)?
    
    
    
    
    
    
    
    
    

end of exam