UV Mapping And You

AsherD · November 1, 2003 8:46 am

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!
Graphic1376.jpgAbout 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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Article Comments

acottted ( posted at 12:00AM Tue, 28 October 2003

This is a very solid, high-quality presentation on an interesting topic that I would like to get, but, it is only useful as a direct-read online - how about setting it as a printer-friendly or some other more-accessable format. Take yourself more seriously, this is good enough to justify saving and reading a couple times to get the fine points - which is not easy to do in its current format. Some of us need to worry on something we know nothing about to get it.

PaganArtist ( posted at 12:00AM Tue, 28 October 2003

This is great. You can never have enough info on mapping. Even the basics are valuable! Thanks!

deemarie ( posted at 12:00AM Tue, 28 October 2003

Hi acottted, Lyrras tutorial can be found, as a printed version, inside the pages of Renderosity Magazine - Issue 3. Every month Renderosity features excerpts from previous Issues of the Renderosity Magazine, to let you preview some of the articles and tutorials. If you would like to receive a printed version of Lyrras tutorial, as well as additional articles, tutorials, interviews and gallery images Issue 3 is still available for purchase through Renderositys Market Place Please note that that all back issues are limited additions and are only available while the supply lasts. Issue 3 Thanks you so much for your interest in the magazine. Dee-Marie Renderosity Magazine's Co-Editor in Chief

hauksdottir ( posted at 12:00AM Wed, 29 October 2003

Gee, I was hoping that you'd use the cat model for all the different mapping formats! (pun inferred). If I was going to add anything, I'd suggest making notes on the map template designating everything... so that a year later, you wouldn't have to remember that the squiggly widgets in the corner were lachrymae. This also goes with templates being supplied to others... are those teeth or are those claws? I bless those map-makers who label things! Carolly

Toyahlean ( posted at 12:00AM Wed, 29 October 2003

This was a very helpful story. very well written and easily understood. Thank you lyrra !!

Lyrra ( posted at 12:00AM Wed, 29 October 2003

For an easier read I suggest the magazine - this is web formatted. waves to audience

Stacey_73 ( posted at 12:00AM Wed, 29 October 2003

Awesome work Lyrra! I have -never- understood mapping.... Ever. And this actually made more than a glimmer of sense... even to -me- and thats saying something. I'll make certain I pick up issue 3 since I'll be needing all the help I can get where this is concerned in the very near future. Thanks for the effort!

Glasko ( posted at 12:00AM Wed, 05 November 2003

I enjoyed it very much! Really explains what you're looking at with each different kind of mapping, nice job.

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