You want to remember that the point of computer graphics is to create a two-dimensional image of three-dimensional objects (it has to be two-dimensional because it's drawn on a flat screen), but you need to think in three-dimensional coordinates while making many of the decisions that determine what gets drawn on the screen.
All of these factors help determine exactly what image appears on the screen.
#Opengl redbook opengl 4.4 how to
This chapter explains how to use OpenGL to accomplish these tasks: how to position and orient models in three-dimensional space and how to establish the location - also in three-dimensional space - of the viewpoint. But how far away from the scene - and where exactly - should the viewer be? We wanted to make sure that the final image of the scene contained a good view out the window, that a portion of the floor was visible, and that all the objects in the scene were not only visible but presented in an interesting arrangement. Obviously, we wanted to look at the corner of the room containing the globe. Also, a particular viewpoint had to be chosen. Each block was carefully positioned in the scene: Some blocks were scattered on the floor, some were stacked on top of each other on the table, and some were assembled to make the globe. The program that produced that image contained a single geometric description of a building block. Look at the image on the cover of this book. You can use the default positioning and vantage point, but most likely you want to specify them. Now you must decide how you want to position the models in the scene, and you must choose a vantage point from which to view the scene.
After reading this chapter, you'll be able to do the following: