In an effort to make this tutorial as comprehensive as possible I am covering some items that many of you may never need to worry about. Creating custom mappings or 'wireframes' to paint for a model is one of those issues. You will most likely come upon this circumstance if you work with a team that is creating new models to add into a game, whether it be professionaly or on an amateur level.  I would recommend that if you are given the chance to create the mappings yourself, then jump on it! No modeler can fully  understands the needs of a skin artist unless he has done some skinning himself. In fact most modelers I've worked with have an extreme shortcoming when it comes to doing the mappings for skins. Even upon giving feedback after feedback to relate the issues that would allow me to create the best skin I often would be handed something that was lacking entirely in its presentation to me.

    It is to everyone's benefit for the mappings on the model to be as good as possible. A bad texture/skin for a model can ruin the whole appearance. No one wants to spend hours of time, to have it sabotaged because the layout of the texture was done poorly.

    But on occaison you will not be able to do the mappings yourself, and in that instance you can use this tutorial as reference for your feedback to the modeler, OR you could point them in this direction to take a look at what I've layed out here so they might better be able to meet your needs.

    I happen to be in a great position here where I have taken up 3D Modeling recently and am doing the mappings for a new model. Therefore I will use that model as an example here that should provide great reference for you when creating the mappings that you need to do in the future!
 

    So lets take a look at the model in question. I've just positioned him standing next to himself here so you can get  a  look at his geometry:

Nothing incredibly exciting, just a normal human male weighing in just shy of 600 polygons.

Now first let me define what I think are the most important factors for your consideration when laying out the mappings for a new skin in no particular order:
 

• Avoiding errors.
• Maximum coverage of the surfaces in the given amount of texture space.
• User friendly mappings that are easy for other people to work with.
• Efficient use of texture size to save memory.
• Proper layout that allows sufficient mapped area for neccesary surfaces.

Avoiding errors.
    I know your saying 'duh!' of course you don't want errors, but this is worth mention as I've seen a lot of mappings that I would consider to be in 'error' where the people who did them had no idea there was a problem. What are some common errors:

• Overlapping areas that should not be overlapped. In other words don't overlap his head over his leg, or anything else of that nature.
• Don't warp the mesh when your mapping it because it will end up getting back to normal shape when its displayed on the model and whatever was painted there will be either compressed or stretched to fit and quite possibly look odd. This does not preclude from uniform scaling (ie: scaling up or down equally in all directions)
• Not mapping visible surfaces. If you do this (depending on the engine) you will get anything from black areas on the model to strange shimmering areas, etc etc.

    I see a lot of mappings done in the neutral position (standing there with hands down near your sides feet shoulder width apart) and the backside right next to it, which ends up only using 70% of the available surface area and looses out on a significant amount of potential for detail. Here are some tips on how to maximize your coverage:
 

• When possible try to use what I called 'mirrored mappings'. In other words instead of laying out surface area for the right leg and left leg individually, create a mapping for the right leg, and then mirror that onto the left leg. This can be done in several ways depending on your program but most support creating the same mapping for the opposite leg and then either rotating or using a 'mirror' function and placing it overlapping the other leg. So you will effectively be painting both at once with the same surface area on the texture.  This only works well though if you have symetrical parts on the model. So if you have a mutant with one large arm and one small arm that have a different number of joints and different muscle bulge areas you arent going to be able to use this technique. Also this is not effective if you want to paint the texture in a non-symetrical manner such as having ripped pants on one leg but not the other.
• Don't be afraid to 'cut it up' this allows you to get much more surface area for certain items especially if your happy with symetrical presentation. So for instance you could cut his head in half and mirror the left over the right and then scale it up (uniformly) 200%. Effectively your taking the same surface area on the image but you will be able to create a much more detailed face.
• Also you can cut up the mappings in other respects like separating the arms, legs, torso and head. This will allow you to position them in effecient areas and unwrap them to cover all the surfaces properly and make more economic use of the texture space.
• Position all your peices like a puzzle to allow each item to be as large as possible in the area given and leave as little blank space between them.

• Consider you may have another person needing to do a skin for you model at some point such as.
• The team or company you are with wants someone else to do a skin for the model. Imagine if your mapping was so convoluted and hard to work with they had it redone and your original work had to be thrown out as unusable?
• If your model is released for public use like a Quake2 Plug In Player Model you will get considerably better reaction to a model that can be easily painted by other people instead of cryptic mappings that they cant figure out.
• There is no real benefit to creating a non user-friendly mapping other than trying to keep other people from working with your material. But if your working in a team environment, of if you ever want to try to work for a company or team environment they may see your work as too hard to adapt to and pass you by.

• Don't create a large texture for a small item. Example: a friend of mine created 128x128 textures for weapons that were to be held in the hands of Quake2 character who would be running across your screen at rapid rates. The size of the actual weapon on screen was fairly small, and with the character standing about 10 feet away (most of the times it they are probably farther away than the equivalent of 10 feet) ..anyways with the character standing 10 feet away and your screen resolution at 800x600 the actual weapon was only about 30x30 pixels total surface area... So here we are using a texture of 128x128 to paint a 30x30 surface area ..that is running across your screen at a sprint? Whats the point. Even if you could see every detail of the weapon if it were standing still right in front of you, its almost never going to be doing that and the space and detail are wasted. Save your texture memory for other items that are either larger or will be seen more often.
• 256x256 is a very large nice area (at the time I am writing this)to map for anything that you might wish to portray a good amount of detail. MANY items will be less. Here are some recommendations:
• Weapon texture map sizes: between 32x32 to 64x64
• Armor texture map sizes: between 32x32 to 64x64
• Power-Ups or Items (box of shells, health etc): 32x32 or smaller possibly. Maybe larger if its an infrequently used item.
• Monsters, Players, Characters: 128x128 or 256x256
• Textures for walls: 64x128, 32x32, 64x64, 8x16, 128x128,256x256 use the size that best fits the texture. Dont make a 256x256 for a button.

    Now lets take a look at the mappings I have created for the model I showed you above. My goals here was to create a detailed face, chest, and back, and reasonable detail for the rest of the model. In this particular instance I plan to paint a bandolier across his chest so I decided not to create symetrical mappings for his chest or back, as well as I'm thinking about a scar down one side of his face so that will not be symetrical either.
 

    So we see on the left hand side the 'wireframe' of the mapings I have created, and on the right hand side we see the texture I've created for it (displayed here so you can better visualize what each peice represents).

    On the right hand side we see his back at the top, and just below that his chest. These I have not utilized any mirroring. Also his face can be see off to the left hand edge, which was not mirrored either, as well as the back of his head. Everything else on this mapping has been mirrored, which effectively gave me almost twice the space!
 

Okay so for explanatory sake let me outline each peice that was mirrored:

• Left and Right sides of head, located just below the face.
• Left and Right forearm just to the right of the face.
• Left and Right bicep to the right of the forearm.
• Left and right foot above the arms.
• Left and right upper legs and crotch below the arms.
• Left and right hand front below the back of the head.
• Left and right back of hands below the front of hands.
• Left and right shin/calf located below the chest.

Finally lets take a look at the almost finished texture mapped and skinned model to see how its turning out:
 

Finally I would like to show some examples of problems that I mention above so you can see what I'm talking about. I don't mean to be harsh here at all about the originator's of these items, in fact most are created by poeple who are good artists in one way or another but there are points worth critiqing, and therefore should be valuable as demonstrations.

Nore PPM:  Mapping Warp due to (non-uniform scaling)

The Nore PPM for Quake 2 was created for the Stand TC for Quake2 by Jon "shine" Jones, and mapped and skinned by Chris "shatterface" Holden.. and addtional skins by yours truly.
 

So here here are our two example skins for Nore showing both the 2D Skin (focused in on the problem area) and the skin on the model.
 

Chris Nore skin (final version)	My nore skin (in progress)
3d shot	3d shot

If you take note of the 2D shots on the top you'll see the skin I created had a uniform metal riveted strip around the edge, and the one that Chris created had a strip around the edge that varies in width. The reason becomse apparent when you display the skin on the model. You'l notice while the 3D Shot of Chris's model still displays some stretching/warping my shot is incredibly worse becaues I was unaware of the stretching that was going to happen when I created the skin. Particularly on the right hand side the metal strip is reduced to 1-2 pixel width when it should be more in the scale of 5-8 pixels wide. This is one of the factors I'm trying to portray in the things to avoid section. Obviously you can work around it, but it takes the artist more time, and multiple revisions to adjust the skin to compensate for warped mappings. A good modeler or skin mapper will hopefully make the attempt over time to reduce or eliminate this kind of problem.

I hope this has helped you learn some of the needs a skin artist will have for when you  lay out your mappings. Please feel free to write with comments, feedback, or suggestions.

Carl  Kidwell
melkior@studio-erebus.com
Copyright 1999-2000