The notion of orientation is vitally important in CG when drawing 3D scenes but, unfortunately, often confusing for the beginner. OpenGL itself makes critical use of orientation to determine the visible side of a surface. Note that the word “orientation” in the current context relates to handedness, e.g., clockwise or counter-clockwise, as we shall see, and has nothing to do with the orientation of a camera as discussed in Section 4.6.3, where the word meant pose or arrangement. The goal for this chapter is an understanding of orientation and its utility in CG.
The first section motivates the concept of orientation with a benign thought experiment. Section 9.2 describes how OpenGL applies orientation to determine the particular ...