Some Cleanup of Chapter 2

• You should definitely read the chapter.
• A primitive is an object that the graphics system can draw.
  • Points
  • Lines
  • Triangles.
• An attribute is a property of a primitive.
  • Point size.
• *GL are described as state machines.
  • This is not the finite state machine from automata.
  • This is a set a value which is used until it changes.
  • Setting the clear color
  • By the way, a uniform variable in GLSL will also be a state machine variable.
• We are working on several different systems of coordinates
• 
• He discusses polygons.
  • When specifying vertexes, be consistent.
    • Always go clockwise or counterclockwise.
    • You will be happy with this later!
  • We tend to like convex polygons
    • A line between any two points, inside or on the edge of the polygon are inside or on the edge.
    • Generally if we don't have this it is problematic.
    • That is a nice property of triangles.
    • This is somewhat hard to test for, so most packages don't
  • We like simple polygons as well.
    • IE none of the edges cross.
    • Triangles are good for this as well.
  • Why?
    • 
    • Even Odd Winding Rule (count line crossings)
    • non-zero winding rule (count line crossings in each direction)
    • Simple, convex -> no rule!