Chapter 4 Perspective, Scene Design, and Basic Animation 109
Perspective
Background models on the 3D game map
are complex as the computer must generate
a game frame that moves in three dimen-
sions. It is really not moving in three dimen-
sions, but rather the computer displays a view
that appears to move in three dimensions. It
does this by using visual perspective. Visual
perspective creates the sense of depth using
shading and narrowing to represent the third
dimension of depth on a two-dimensional
screen. Important to visual perspective is the
concept of a vanishing point.
A vanishing point is the point in the back-
ground where edges of all assets will meet at a
single point if extended. A rectangular surface will
appear pinched into more of a triangular shape. In
other words, parallel lines do not appear parallel.
Notice how the road in Figure 4-20A appears
to narrow and darken as it recedes into the background. In the far distance,
the road vanishes to a single point. In Figure 4-20B, you can better see
the vanishing point. By blocking out the background images, you can see
the road appears to form a triangle. The farthest point in the distance—the
vanishing point—is the top of the triangle. Of course, the edges of the actual
road remain parallel, they just appear to meet in the distance.
If you look more closely at the picture, you will also see that the tree tops
and all other “north/south” objects vanish to the same point. In Figure 4-20C,
red lines are added to the trees where the trunk meets the branches and to
the road edges. You can clearly see all objects recede to the same vanishing
point. In this case, the vanishing point is centered in the middle of the view.
This scene is now divided into four triangles of visual perception.
Figure 4-19. Models are 3D assets. They have length
(X), width (Y), and height (Z) dimensions. (Model courtesy
of Autodesk, Inc.)
A B C
Figure 4-20. A—The vanishing point is clearly visible in this photo. It is in the middle of the image. B—If the trees and
sky are blacked out, the point where the edges of the road converge is obvious. C—Red lines are added to show the
receding lines on the road and trees. The receding lines converge at the vanishing point.