Creating and Editing Texture Coordinates (UVs) - An Introduction to Computer Graphics for Artists - page 169

10.4.10 Options

The point of providing such a wide variety of options for something as simple as a
sphere is to get you thinking of the possibilities available for the more complicated
models you are likely to make. There are many options available, even more than are
represented here for a simple geometric primitive. Imagine the number of options for
a character, or a skyscraper, or an automobile engine. Notice too, that the type of
sphere affects the mapping results. Think of the difference between a geodesic, polar,
and cubic sphere. The results are not the same. When you model, be aware of the
impact your modeling decisions have on the eventual mapping of your object.

10.5 Editing

UV editing, unlike projection, is where the hard work of texturing a model is done.
It is here that a texture map layout is decided on and here that an artist succeeds
or fails to make the best use of the pixels available for texture maps. In Sect. 10.2 ,
different projection methods were described as an introduction to concepts related
to UV editing. To illustrate the different projection methods, some discussion of
editing took place, but not a great deal. This chapter explores fi ner details of the UV
editing process not covered earlier.

10.5.1 Balance

The goal of any good UV layout is a balance between distortion and seams. To
achieve this, artists must decide which is more important and what the effect
will be on the texture artist. The object itself will always dictate your limits,
and every object is different. As a general rule, the simpler an object is, the easier it
is to map. That said, curvature, insets, and extrusions add seams to any UV layout,
even on simple objects.

10.5.2 Modeling Technique and UVs

Some objects should not have their texture coordinates projected onto them after
the model is fi nished. This is because some shapes are better off with their default
coordinates. Think of a table cloth as a fl at grid subdivided with several hundred
polygons. As a planar rectangular object, its default UVs will be distortion-free and
effi cient. 100 % of the available texture space will be used. Now imagine the same
cloth dropped onto a table. The corners will now fold in undulating patterns and
some cloth will fall over each of the four sides of the table. Any attempt to project
new coordinates on this object will be more complicated than it would have been
before the cloth was dropped onto the table.