Modeling 1: Polygons - An Introduction to Computer Graphics for Artists - page 78

Another thing to be aware of when using Boolean tools is that they are very
picky. The geometry you use for the operation should be as clean as possible. All of
their normals should be facing the right way, non-manifold geometry will not work,
and cracks or gaps in either polyset will also cause problems. Likewise, unmerged
vertices, non-planar n-gons, and just about any other error described in Chap. 10
could have unwelcome results in a Boolean operation.

6.3.5 Object Types

Some objects are simple objects , meaning they can be built in a single operation,
without editing. Other objects are compound objects , meaning that they require a
combination of polygon creation tools, editing, or both. Most objects in CG are com-
plex. Some forms of dinner plates, or a saucer from a cup and saucer pair, are excellent
examples of simple objects. These objects can be built from a single profi le curve
rotated 360° around an axis. A more complex object is a fork or a spoon. In both cases,
there is a difference between the shape of the handle and the business end of either
instrument that requires more than one tool to create. You should learn to recognize
the difference between simple and complex objects, but to help you do that, you
should have an idea what the various common tools do and how they are used.

6.3.6 Box Modeling

Box modeling has become a popular method for building complex objects com-
posed of many parts, like characters and architecture. Box modeling, as stated in
Sect. 6.2.1.1 , has some serious drawbacks in connection with model optimization
and also with fi delity to the source material. It is not only more accurate to model
two boards that are attached to each other as two separate boards rather than a single
object of the same shape, but it is more effi cient as well. One advantage box model-
ing has is that it is easy to use the geometry of the object as a reference to create
other parts of the structure. In the example of a building, a cube can be scaled to fi t
the bounding volume of the target object and then subdivided to fi nd the correct
location of windows and doors. The result is a single infl exible object, but it can be
a quick way to fi nd measurements while modeling a complicated structure.

6.3.7 Part Modeling

Part modeling is the alternative to box modeling. Instead of thinking of your model
as a single complex object, you think of your target as many separate parts that
have been assembled into a complex structure. Each part will always be simpler
than the entire assembly because the full assembly includes every part. This makes