CG Basics - An Introduction to Computer Graphics for Artists - page 13

Fig. 2.5 A vertex in space

2.3 Interfaces for CG Artists

2.3.1 Navigation Within an Application

CG applications vary considerably in some respects, but they also have much in
common. Some programs have specifi c commands that are not a part of any other
program, but most programs have the same basic tools. They also have very similar
methods of viewing what is going on inside their virtual 3D workspace. Despite
their variations, all animation applications do pretty much the same thing; they
allow a user to create a 3D fi le through a graphical user interface (GUI). Therefore,
the two things that a user needs to know in order to make a 3D object for a CG
animation are the basics of 3D and the GUI for the software they are using.
When you fi rst open a 3D application, you will see a window called a viewport
that has a representation of world space drawn within it. On the screen, world space
usually looks like an origin icon plus a grid. Depending on which viewport you are
looking at, orthographic or perspective, you may be looking at a fl at grid made of
perpendicular angles, or a grid made out of convergent lines that can be twirled
around in 3D (Fig. 2.6 ). An orthographic grid is drawn perpendicular to the ortho-
graphic camera, and the perspective grid is drawn to a vanishing point based on the
position of the perspective camera. Depending on the focal length of the virtual
camera, you may notice that the convergent lines in the perspective window are
curved. This is because a short lens causes more distortion than a long lens, and at
the same time it fi ts a wider viewing area into the same amount of space (Daloukas
et al. 2008 ). This effect is noticeable in photographs, but less easily detected when
observing our environment because we are accustomed to focusing our eyes in the
center of the fi eld of vision (Hopf et al. 2006 ).