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UV Mapping Tips And Tricks
Organic Model Mapping Creating texture maps for organic models is easy in some respects, but it does come with its own pitfalls. First, you're bound to encounter some crazy shapes when mapping an organic creature. But the blessing is that you can get away with much more warping in the mapping because of the model's curvy nature. Continuous mapping is definitely a key technique you should use when mapping organic shapes. Keep an eye on your seam count and look for ways to just unify everything into a continuous map, while using as much of the texture space as possible - this is almost an art unto itself.
Technical Model Mapping Technical objects are actually fairly easy to map. The difficult part is organizing and optimizing the layout for the poor texture artist. All the texture artist gets is a giant, colored puzzle, and he'll spend hours trying to figure out where every part goes. There are some simple rules to follow when mapping a technical shape:
UV Mapping With Shader Effects In Mind Shaders are a welcomed change in the world of gaming. John Carmack really introduced the concept and his artists took full advantage of it. Quake 3's characters and environments greatly benefited from the use of shaders. From cheating effects like cascading waterfalls to the patterns of energy running through the outer layers of mech armor plating in Zone of the Enders, shaders have opened up a new range of visual possibilities for artists everywhere. All you have to do to achieve these effects is follow some basic mapping rules. Say, for instance, you want to create a flowing river that wraps around objects that get in its way. All you have to do is decide which direction the water will flow, and then orient and distort your mapping to help achieve this. The picture below illustrates the mapping and final look of the effect. All I did was straighten out the more curved areas so that when the shader is applied, it will looks like it is actually flowing around obstructions. The same rules apply for things like tank treads and billowing smoke, which were created with polygons instead of particles in Freedom Fighters. The game just used a simple scrolling texture with the model's mapping oriented to take advantage of it.
Blended Detail Textures With Layered Materials A detail texture is a texture that's blended over another texture, to a degree that's based on your distance from the object. The advantage to this is that you can cheat a lot of micro details without actually having to use a massive image. For instance, imagine you have a brick wall that's 256x256 pixels in size, and another one at 128x128. The smaller one would be used for the detail texture. Usually when you start getting really close to a wall it starts looking blurry, but when the bigger texture is used in combination with a smaller detail texture that fades in when you get closer, it gives the illusion of greater detail. There's another use for detail textures as well, which requires some programming to create a pixel shader for your game engine. Using a shader, you can use up to three different detail textures at the same time on a model, using either vertex colors or an extra texture to define the blends. You use the RGB color values in the picture to define the blends, and each color value coincides with one of the detail textures that you define in the game's material system. This permits smooth blends from one detail texture to another, because it checks the RGB level. (Black, of course, won't show up at all.) The figure below shows a color example and the final results when using the detail textures in conjunction with a color map.
And the final bend of the face itself:
Renier's Texture Mapping Process No I'll explain a method that I developed for UV-mapping objects in 3ds max. It takes a little work to get use to, it but once you're accustomed to it, you may never map objects the same way ever again. Think of it like skinning an animal, then removing the skin, laying it out on the ground, and painting it. To begin the process, I clone the object and then take it apart manually in 3ds max. Then I organize it and apply mapping to it, saving that out to a separate file. Finally, I select the original object and load the mapping data from the cloned version. That's an overview of the process, now let me explain it in more detail. Things To Keep Track Of Keep the same polygon count. The polygon count of your object needs to stay the same as the original from which you cloned it. When doing the final welding, make sure you don't accidentally delete or merge any polygons. Otherwise your mapping will fail to load and you'll need to do it all over. Save regularly and keep an eye on that polygon count every time before you save. Detach to same object. When breaking up the model into the desired sections that you want to map, make sure that you detach it to the same object. Otherwise you will remove polygons, and the object's mapping will become invalid and you won't be able to load it back onto the original mesh. Mapping by hand Clone object. The first step is to create a clone from the original object. Write down its polygon count and put that aside for later reference. Next, hide the original mesh because you don't want to edit it -- you're going to be taking the cloned mesh apart and you don't want to change the original.
Fragmenting the Object. Since this is a symmetrical mesh, there is no reason to map both sides at the same time. So before you clone the mesh, delete the right side of the head. Just map one side and mirror its mapping to the other side. Now the mesh is ready for mapping. Hide the original mesh, start taking the clone apart. In the image below you can see I've isolated the ear, the inside of the mouth and the front area of his hat to be the first areas to cut.
The beauty of this process is that you have all the modeling tools at your disposal when taking apart the model. Simply pick a viewport that you want your polygons to face and then start taking the mesh apart, arranging the polygons to face in the desired direction, as shown in the figure below.
As you can see, I started detaching the polygons and made them face the viewport as much as possible. This ensures an accurate pixel density for all the objects I map. Make sure you haven't deleted any polygons in the process. Next we move to the face. In the next figure, I've highlighted the sections that I plan on breaking apart:
I begin detaching them from each other, orienting them towards the viewport at the optimal angle. I keep an eye on my polygon count just, to make sure I haven't deleted anything, then save the scene in case my PC crashes. As you see in the next figure, the mesh is very fragmented. That's not a problem, though - I will take care of this eventually.
Now that everything is detached and laid out nicely, we can begin to organize it. I keep to a 1x1 aspect ratio for the layout since this model will be used for real-time game graphics. After moving around some polygons here is the end result:
Reassembling the Puzzle. Now that it's organized, it's time to weld the polygons back together again. This process is simple and doesn't take much time. Just keep and eye on the polygon count when merging the vertices. After some welding, here is the final result. Now it's time to transfer the mapping over to the final object.
Transferring mapping. Select the mesh and apply the planar map to the model. Now that it has mapping, apply the UNWRAP modifier. This is the modifier I use to load and save the mapping of the model. Click and save mapping for the mesh. Saving and Loading mapping. Next, unhide the original model and apply another UNWRAP modifier to it. Click on "load" and then apply the mapping from the cloned model onto the final mesh. Click on "Edit mapping" to check if the mapping loaded properly.
If all went well, you have a model with accurate mapping. Enjoy your newly mapped model! ______________________________________________________
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Introduction
GDC
2004 Feature 
