BOM and Bento
This discussion will have to cover a little bit of Second life history and will edge into a few technical topics.
It all started many years ago, with the first Second life avatars, and the file format that these 3D objects were saved with. The original avatars were fairly low resolution (mesh complexity, also called "Level of Detail (LOD)). Over the years, this avatar has been referred to as "The Classic Avatar", and is still the default avatar people receive when setting up a new account. The new format is now called "Mesh". The Ultra Vixen is a mesh avatar.
Each avatar body was, and still is composed of a number of components.
At the heart of it all is the Armature: The armature, also often called the bones, are just what it sounds like. Each bone is connected in various ways to make up a complete skeleton that can be animated to give human like movement. Each bone is programmed with a particular strength to hold and deform the 3D mesh that it is assigned to. This is called the "Weight Painting" since painted color patterns during the modeling stage of 3D mesh creation are translated into how much the mesh is "grabbed". The Edit My Shape window within the Second Life viewer also stretches these bones to create custom body shape files. Note that these saved body shapes are a distortion of the original shape of the mesh, from how it was created in the 3D creation software. I use BLENDER to make all this stuff.
The Shape File: As stated above, the shape file is created by adjusting the Edit My Shape sliders, and then saving this with a new file name. A Second Life avatar can not exist with out a worn Shape file. You will always have one shape file on, and it can not be removed. But putting ON a new shape file detaches the one previously worn.
The Mesh: Either Classic or "Mesh" is the 3D "frame". The frame is made up of vertexes, which are simply a point in 3D space. It takes two vertexes to make a line or edge. It takes three points to create a surface. Many points create many surfaces. 3D model creators build up these objects to make everything you see in 3D video games and movies.
The Skin: The skin is a 2D graphic file that is "Wrapped" over the mesh. The easiest way to think of this - is like taking the skin off an orange. No orange is actually perfectly round, so that skin can only be put back on in one way to be correct and fit without distortions. All mesh must be "Unwrapped" to create a flat "Texture Map". That texture map gets imported into a program like Photo Shop or GIMP (2D graphics software) to have a design painted onto it. Then imported back into the 3D app or into Second Life to Apply to the body mesh, or 3D clothing, or what ever other things creators create.
The Physics: This is special script that creates small scale local animations withing individual sections of the body mesh, designed to mimics Gravity, Weight, Inertia, etc. When created correctly for each brand of body, people will see natural looking bounce and jiggle though appropriate body parts. There is a caution here to be aware of however: every body mesh is made by different creators and is weight painted differently. This means various brands of bodies and even the three versions of the torso I created will have different degrees of stiffness (or looseness). Physics must be matched to the body worn. I supply physic that are design just for the Ultra Vixen. Please use these.
Bento is an expansion of the Armature system. The original Second Life armature had enough bones for average body animation and a few simple face animations to create a simple smile or moving the eyes. Since there are no muscles, all movements within the face also have to have bones to grab the mesh and simulate movement to create expressions. The original hands also could not be animated, with movement at the wrist being the only options. Mesh creators actually resorted to modeling different hands for various hand poses - like a clenched hand or a relaxed hand. Many people also like to use an avatar that looks like an animal (a furry) or an Angle. Animating hind legs or wings was a real problem.
The creators of Second Life addressed this by greatly expanding the Armature. The new "Bento" armature includes bones for each segment of the fingers, for sections of a bird's or angle's wings, for hind legs, and many more bones within the face. In turn this has meant a new generation of mesh bodies, and also for new products from pose or animation creators. New dances that include Bento data will move the fingers and sometimes change face expressions also. For people customizing their shape files, it has meant a greater freedom to shape your face closer to how you envision yourself looking.
The Ultra Vixen mesh body and head has been design around the Bento armature, and will show face and or hand animation while using an AO or moving pose, that includes Bento Data.
BOM means Baked On Mesh. Which actually means you can layer a number of graphics images - like a stack of images painted on glass and looking through the pile. Second life includes an array of image types that can be used with an avatar. How these were able to be used was dependent on the type of avatar you used, Classic or Mesh, and if you used mesh clothes or simply used System Clothes.
All avatars require an armature. The first mesh body creators depended on a type of clear graphic file called an Alpha, who's role was to hide the default Classic avatar, yet retain use of the armature. Then a mesh body part could be worn attached to the bones of the armature and used its own graphic file to apply a skin or tattoo, etc. The problem with this was that the 2D graphics images that were used with the classic avatar to create the look of human skin or animal fir, clothes, tattoos, scars, wet look, etc, were not able to be used with most mesh products. These graphics are called System Skin, System Tattoos, System clothes, and have associated icons beside the file names in each account inventory.
A result of this new second standard, was that when people migrated their avatars to mesh, the previous inventory could no longer be used. Many people deleted all that old stuff, self included. Others had a clutter of unused inventory. Since many of those products remained on sale, it also lead to confusion for new Second Life users.
The new BOM standard is a complete replacement of the classic avatar by any BOM enabled mesh avatar, while system graphics see both formats the same way. This gives new life to old system clothes and skins, etc. It means mesh bodies can be made simpler enabling faster load times and less lag while being able to wear any system skin or clothes, at the same time as wearing mesh clothes over top of the body surface. A common strategy is to wear system graphic lingerie or nylons under mesh clothing. It also means that any system skin can be worn, eliminating having to wear dedicated skins for specific brands of mesh bodies. Just find the skin in your inventory and click WEAR. Simple as that. Any other graphics could be layered on top with the use of the ADD method of wearing things. As you add additional system tattoos, or clothes, the computer will take a moment to figure how how these graphic interact, sometimes turning your avatar gray during the calculation. When the "Bake" calculation is done, you will see your avatar with the new changes you selected. BOM makes Second Life so much simpler! People who have tried BOM bodies love it.
The Ultra Vixen body is BOM enabled going even one step more simple and not requiring any sort of BOM relay. The only thing that sometimes messes up people trying a BOM body for the first time, is that they forget to remove their Alpha from previous mesh bodies, or have even forgot where in their inventory it is located. Start with a clean nude classic avatar and then wear all the parts in order. Wearing the Ultra Vixen for the first time should only take a minute or two - it's that easy.