CPSC 324, Spring 2001                         Information For First Test
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The first test for this course will be given on Thursday, February 23.
Here is a list of some of the terms and ideas that you should be familiar
with for this test:

  computer graphics                  GLUT API functions:
  painting programs                     glutInitDisplayMode()
  drawing programs                      glutMouseFunc()
  pixels                                glutKeyboardFunc()
  geometric modeling                    glutReshapeFunc()
  attributes (such as color)            glutDisplayFunc()
  rendering                             glutIdleFunc()
  geometric transformations             glutPostRedisplay()
  computer animation                 
  OpenGL                             OpenGL API functions:   
  GLU                                   glVertex3f, glVertex2f
  GLUT (why does it exist)              glRectf
  Mesa                                  glColor3f
  single-buffered graphics              glClearColor
  double-buffered graphics              glClear
  vertices                              glViewport
  3D coordinates                        glBegin, glEnd
  polygon                               glFrustum
  convex polygon                        glOrtho
  color                                 gluLookAt
  RGB color space                       glTranslatef
  HSV color space                       glScalef
  indexed colors                        glRotatef
  modeling transformation               glMatrixMode
  translation                           glPushMatrix
  scaling                               glPopMatrix
  rotation about a point in 2D
  rotation about a line in 3D        Constants for glBegin:
  projection transformation             GL_POLYGON
  perspective projection                GL_POINTS
  orthogonal projection                 GL_LINES
  clipping                              GL_LINE_LOOP
  view volume                           GL_LINE_STRIP
  combining transformations
  OpenGL as a state machine
  camera analogy for 3D viewing
  viewing transformation
  wireframe
  RGBA colors
  about the GIMP:
     filters
     brushes
     gradients
     gradient tool
     color blending and opacity
     selection tools
     selecting by color
     layers
     
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Here are a few questions from tests given in this course in
previous years:

1.  An OpenGL program has an "idle" callback function that includes
    the command "spin += 2;", where spin is a global variable.  Here are
    two display functions that could be used in the program.  Describe
    and/or draw the animations produced by each, and explain the difference.
    (Assume that the clear color is white, the drawing color is black, and 
    the projection was set with "glOrtho(-5,5,-5,5,-1,1)".)

   void display() {                      void display() {
      glClear(GL_COLOR_BUFFER_BIT);         glClear(GL_COLOR_BUFFER_BIT); 
      glLoadIdentity();                     glLoadIdentity();
      glRotatef(spin,0,0,1);                glTranslatef(3,0,0);
      glTranslatef(3,0,0);                  glRotatef(spin,0,0,1);
      glRect(-1,-1,1,1);                    glRect(-1,-1,1,1);
      glutSwapBuffers();                    glutSwapBuffers();
   }                                     }

2. This question uses the following object:

         (OBJECT NOT SHOWN HERE -- MAKE ONE UP)
   
    a) Show how this object will appear in OpenGL if it is drawn as a
       wireframe model and the following command is used to set up the
       projection transformation.  (The default viewing transformation
       is used, with no modeling transformation.)
       
               glOrtho(-3,3,-3,3,-3,3);
               
    b) Repeat part (a) using the following commands to set up the projection
       and viewing transformations:
       
               gluLookAt(0,0,5, 0,0,0, 0,1,0);
               gluPerspective(45,1,1,10);

3.  What OpenGL code would you use to draw a red triangle that lies in the
    (x,y)-plane and has vertices at (-1,-1), (1,-1), and (0,2) ?
    
4.  Before a scene is displayed in OpenGL, it is clipped to the view volume.
    Explain what this means.