116 Video Game Design Foundations
What Is a Mesh?
All 3D objects are made from intercon-
nected polygons stuck together to form a shape.
These polygons, or polys, stick together along
their edges and vertices in what is referred to as
a mesh. Creating a mesh is like gluing all of the
pieces together to make one object. However,
the computer does the “gluing” based on the
size you give the object.
The mesh provides the shape for an object,
Figure 4-31A. After the mesh is complete,
textures, called materials, need to be applied,
Figure 4-31B. Often, a single 2D texture map
contains more than one image, Figure 4-31C.
Once the texture map is wrapped onto an
object, the images are aligned to create the
fi nished object, Figure 4-31D.
The poly count is the number of polygons
used to make a 3D object. This number is a crit-
ical measurement. The more polys, the more life-
like the object becomes, Figure 4-32. So, why
not make all objects with a high poly count?
Simple; every polygon needs to be morphed
as the object is moved. The computer needs to
calculate the change in distance between each
vertex of the polygon as the object gets bigger,
smaller, and moves to a different view. If every
object has a high poly count, it would take an
enormous amount of time for the computer to
render the objects as they move. Some proces-
sors would not be able to keep up with the
calculations. On these systems, the view may
skip, play slowly, or appear to have glitches.
Look at the example of the expanding-ball toy. Imagine how long it
would take to calculate the change in distance between every vertex each
time the ball changes shape. The computer must do just that. The more
polygons, the more vertices and the harder the task.
The color and texture maps assigned to an
object tessellate around the object. Each poly
has a piece of the texture image on its surface,
like a mosaic. See Figure 4-33. The amount
of tessellation is controlled by the number of
polys on the object. The higher the poly count,
the greater the tessellation. Therefore, the
higher the poly count, the smaller each slice of
the color or texture map.
A
B
Figure 4-30. A—Notice the black and white shapes on
the surface of the soccer ball. These are regular polygons fi t
together to simulate a round shape. B—Notice the faces on the
geodesic sphere. In this example, they are regular triangles.
These are fi t together to approximate a round object.
CHEAT CODE: MOSAIC
A mosaic is a design created by placing
colored tiles, stones, or glass in a pattern
to make a picture. This relates to 3D
models because the model uses
colored polygons to create an image
just like the mosaic picture.