Coordinate Systems

Some coordinate systems used:

• Desktop coordinates
  • Origin at upper left corner of screen
  • +X points right, +Y points down
  • 1 unit = 1 pixel
  
  
• GLUT pointer coordinates
  • Origin at upper left corner of window
  • +X right, +Y down
  • 1 unit = 1 pixel
  
  
• Default OpenGL drawing coordinates
  • Origin at center of window
  • +X right, +Y up
  • 1 unit = 1/2 width or height of window