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Video Game Design Foundations
programmed to resize, re-shade, and shift view in relation to the camera. In a
2.5D game, however, multiple poses are used. These poses change similar to a
2D character, but each sprite has a 3D appearance.
To create a sprite character set for 2.5D game, the characters and obstacles
are all generated with length, width, and depth. Multiple camera angles can be
used with a 3D character to produce a character that works. The character will
need to be designed so it can be seen from all of these different angles. Most
game designers create these simulated 3D characters with a minimum of 26
viewing angles for each pose. Highly defined characters may have more than
100 viewing angles for each pose.
In some 2.5D games, the character set is replaced with actual 3D models
with full articulation.
Full articulation
means all of a character’s body parts
can move through a range of motion in a realistic manner. In these games, the
background is still flat and two dimensional, but the characters and interactive
objects are true 3D models.
Three-dimensional (3D) games
have 3D characters and 3D background
objects called models. Recall from Chapter 1 that models are different from
sprites. Sprites are defined in two dimensions (X and Y). Models are defined in
three dimensions (X, Y, and Z), as illustrated in Figure 4-24. They are computer
generated in real time to show the correct angle and pose. It takes a lot of
computer processing to make a 3D model move.
The discussions in the following sections are actually oversimplified
explanations of how perspective, pixel shading, vertices, scaling, and depth
work within a game. However,
these discussions should give you a
good idea of these concepts that are
used to make a 3D scene in a game.
Perspective
Background models on the
3D game map are complex as
the computer must generate
a game frame that moves in
three dimensions. It is really not
moving in three dimensions, 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.
Three-Dimensional Games
Figure 4-24.
Goodheart-Willcox Publisher; model courtesy of Autodesk, Inc.
Models are 3D assets. They have length
(X), width (Y), and height (Z) dimensions.