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Chapter 4 Perspective, Scene Design, and Basic Animation
the 3D engine can resize the sphere by changing the distance between the vertices.
This is also how facial features and other rounded character assets are resized.
The type of sphere described above is called a
UV sphere.
The name comes
from the process needed to wrap a texture map around the object. A 2D image
is stretched around the sphere, as illustrated in Figure 4-33. U is the same as X
and V is the same as Y. In some applications, a third element (W) is added for
the Z dimension.
Figure 4-32.
Goodheart-Willcox Publisher
A—The character is viewing the cube from one angle. B—As the
character moves, the 3D engine moves the vertices on the cube. The
original vertices are shown in blue and the new locations are shown in
red. Notice how the lower-right vertex is now visible to the character,
but the lower-left vertex is no longer visible.
Figure 4-33.
Goodheart-Willcox Publisher; texture provided by NASA
A—This is a 2D texture map of Earth. B—To create a model of Earth, draw a sphere.
C—The texture map is wrapped onto the sphere to finish the model of Earth.