The best-made texture in the world will be of little use if the
model is not mapped well. (
I recommend using a UV mapping
program such as Steve Cox's UVMapper, which can be downloaded as
freeware: www.uvmapper.com). When a 3D mesh
is assigned UV coordinates, each facet of the mesh is mapped to a
specific place on a flat plane. This allows the artist to paint on
a flat digital surface, and have the texture show up in specific
places on the model. Problems can occur with this method, since
most curved surfaces are hard to peel, getting all segments flat
and undistorted. All UV mapping requires some amount of compromise.
Any time you want more control over your texture, UV mapping is
essential. To start off you will need to UV map your model. There
are a number of considerations: when to map, how to map and how
many maps. Many modelers believe that mapping "as you go" is more
efficient than mapping it all at the end. Also, if you are
deforming a flat surface, mapping the surface before deforming
gives you a nice flat texture to paint on. However, mapping
afterwards has its good points as well. Often modelers do not know
how much a model will evolve during the process it is quite
possible to delete or cover up something you made earlier. Most do
agree that assigning and naming materials during creation makes it
easier to map, and saves times if converting to Poser formats.
Also, UV mapping, naming materials and groups as they are created
saves you from having to play the "Name That Thing" game. Decide
whether your model should be mapped in one solid piece, or with a
separate texture for each piece or side. Many Max and Lightwave
users prefer multiple maps, although most Poser-ready characters
and objects are single-mapped. Some Artists feel that giving the
object one unified texture map to cover the entire model makes it
easier for people to create and apply new maps. Single textures
have been the standard for most Poser figures. Single maps do have
their drawbacks. It is difficult to change just one piece of the
texture quickly. Also, it can be quite difficult to map everything
optimally, especially when the model needs different types of UV
mapping for different areas. Size and resolution become an issue as
well. In order to cover an entire model, the pieces on the template
are fairly small, which means the single texture file itself has to
be bigger. Not all machines or applications can handle a 10 meg
texture file, especially when several such textures are used to
customize a figure. If one 10 meg texture is used for the skin, and
another for the eyes, the program may have to read 20 megs of
textures. This can be a tremendous drag on system resources,
especially for animators. Many 3DS and Lightwave modelers feel that
multiple maps are easier and more flexible. Each piece is mapped
separately, and each has its own texture. This can make it
extremely easy to change just one part quickly, or to adjust the
mapping of one piece. Unfortunately, with multiple maps, a single
table model could have anywhere from one to as many as 30 or more
textures, especially if each piece also has bump and reflection
maps. It can be extremely time-consuming and confusing to re-apply
textures to such a model, or to figure out which goes where if the
naming is not extremely clear. Most modeling programs have UV
mapping capabilities built in. There are also a number of third
party mapping programs that also map objects. Most modelers prefer
to use the built in mapping in their program. This gives the
ability to map as they build, and to change things very quickly and
easily. However, the mapping can be lost when exported, depending
on the output format. Since your model is a three-dimensional
object, there are a number of different approaches and methods to
'peeling' it. Certain methods work better on a particular model
shape than others. Many organic shapes are very difficult to map
well, so a combination of approaches, plus judicious mesh
spreading, may be needed. You want simple pieces, as flat as
possible, with an even mesh, and seams in less visible places.
Planar is the most commonly used method of mapping objects.
Planar mapping splits your model into 'front' and 'back', depending
on the angle you are viewing it from. Many character skins start
with planar mapping; with mesh spreading used on the edges to
uncompress the mesh segments. Animals are often mapped from the
side, so a seam runs down the spine and the middle of the face.
People are often mapped face-on, so the seam runs around the face,
down the sides of the neck, tops and bottoms of arms, side of
torso, sides of legs. Planar is also useful for anything that is
flat.
Box mapping is the second most commonly used mapping, and
most common for rectilinear objects. Picture a cardboard box. Now
cut it apart at every edge. You will end up with six pieces four
sides, top and bottom. For objects that are cubical or rectangular
this is the most efficient mapping. This is also the best place to
start when examining a mesh for the first time.
Sphere, think of a globe. Cut it open from top to bottom,
and along each latitude line on top and bottom. When it is spread
out flat you will have a rectangle, with little saw-teeth at the
top and bottom where the north & south poles were. Sphere maps are
twice as wide as tall. There will be some distortion at the tops
and bottoms when mapping spheres.
Cylinder, imagine a tube cut in a straight line down one
side and flatted to create a rectangular surface. If the object is
not hollow there will be smearing at the tops and bottoms of the
cylinder so only use if the ends of the object are hidden.
Cylinder Cap is the same as cylinder, but the ends of the
tube are mapped separately. This enables the texturing of the ends
of the object without distortion. Although most objects respond
well to one kind of mapping, a complex object can have pieces that
are best suited to different mapping techniques. Do not be afraid
to experiment with different parts of your model in order to
achieve the best map possible. The goal is to make a texture with
as few pieces as possible, making sure every surface has a flat and
even mesh. Many models available for free download have mapping
issues. Often they do not have mapping coordinates at all. If you
re-map a model with the intent to distribute texture, people will
need your new version with the new UV information in order to use
your templates and textures.
Remapping Models -- Copyright
Issues This also involves copyright issues. Make sure to check
distribution rights with the creator
before making your new
version available. Many free models cannot be redistributed, so you
will have to get the maker's permission, in writing, before doing
so, to protect yourself against future legal action. An alternative
is to distribute the UVS information, which can be reapplied using
UVmapper but does not distribute the copyrighted mesh itself. The
drawback here is that novice users may have difficulty setting
things up properly, so if you choose to use the UVs method, make
sure to write a thorough readme file. These are just the basics of
Uvmapping, and of course the best way to become proficient with any
program is to practice!
About Lyrra: Lyrra Madril is a professional
freelance graphic artist and trainer. Previously from New York
City, currently living in Delaware, Lyrra has had over ten years
experience using and teaching various graphics packages in the
advertising and corporate illustration business in NYC. Lyrra is
also the Senior Poser Moderator here on Renderosity. In addition to
digital art, she also makes Rennaisance costumes, custom
VolksWagens, miniature dolls, crazy quilts, oil paintings,
handdrawn science fiction/fantasy images and writes and composes
songs. Lyrra is currently teaching online Poser and Bryce classes
at
LVSonline.com.
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