The question keeps coming up in the SL Forum, what is a mesh body and why won’t my clothes show? I am so confused… Yeah, I can see how that would happen. So, I need something I can link them to. This is the ‘something’. I’ve tried to keep it simple for noobs without 3D modeling experience.
To understand Classic and Mesh avatars one has to understand Second Life™ has a history and understand some of the basics of 3D modeling.
SL Started in 2003, 2004 depending on what you define as ‘starting’. It started with a basic avatar that evolved over time. That is the Classic avatar. It is still with us.
If you take off everything your avatar is wearing that you can take off, you are looking at the Classic avatar. You can click the top menu Developer (press Ctrl-Alt-Q to reveal the menu item if it isn’t showing)->Avatar->Character Tests->Test Male/Female. This will set your avatar to the very basic (Classic) default-test avatar known as Ruth or Roth.
If you press Ctrl-Shift-T, you can see that everything in SL is mesh (wireframe image above). What may not be obvious is the things we call primitives or prims, for short, are mesh too. These are things like the classic avatar, cubes, cones, spheres, etc. The mesh part, or list of vertices/polygons, of these prims are built into the viewer and are part of what you downloaded when you installed the viewer.
These are parametric primitives. This means that all the cube-prims in SL use the same mesh which is built into the viewer. The different sizes and colors of all the cubes are controlled by parameters. Only the parameters are downloaded when your viewer needs to render a cube. This process was created when the Internet was SLOW to allow better performance. Building them into the viewer saves downloading lists of vertices.
For avatars, the built-in mesh was personalized by what we call SHAPE. An SL shape is a set of parameters for the face, body, feet, etc.
There are some milestone points for changes in the SL system. Understanding those helps one understand the avatar we have today. It also helps when you have to figure out which tutorial is useful and currently meaningful.
A big change was the addition of a new prim we call ‘mesh’ in 2013. This can be confusing as everything in SL is mesh, a group of polygons. A ‘mesh’ prim is a prim that does NOT have its set of vertices/polygons built into the viewer. The list of polygons making up the ‘mesh’ item is downloaded from the asset servers as needed.
We can build those vertex/polygon lists using 3D modeling programs like Blender.
Once the feature was added to SL people begin making mesh clothes. A significant problem of the era was the Appearance Sliders used to make an avatar shape did not affect the mesh clothes, just the avatar body. Finding clothes that fit was a headache. The solution was what we call Standard Sizes. Clothes were made to a standard set of sizes. If you set your avatar to one of the 5 standard sizes the clothes would fit, mostly.
The next milestone was the creation of Fitted Mesh, added about 2014. Clothes could be made as Fitted Mesh and the shape sliders would change the size of the fitted mesh clothes. It became much easier to make clothes that actually fit. But, it was still a headache, just a smaller headache.
Fitted mesh clothes just didn’t fit Classic avatars all that well. Because of technical complications, the avatar shape and fitted mesh clothes’ sizes grew and shrank at different rates when the Shape Sliders were changed. If you wanted a fat or skinny avatar, it was almost impossible to find clothes that fit. One had to stay in the middle ranges of size for a good fit.
In 2015 and 2016 creative people made fitted mesh bodies that were the same type of mesh as fitted mesh clothes. So, they both responded to the shape sliders at the same rate. This means the same clothing item for a skinny avatar, average avatar, or fat avatar pretty much fits. Thus, the popularity of fitted mesh bodies… plus a number of other technical factors and better looks.
A fitted mesh body, hands, feet, and head are all mesh primitives used as attachments to the Classic avatar. They cover the Classic avatar body. They hide the Classic body.
Because a mesh body fits the classic body so closely, like a second skin so to speak, the classic body tends to poke through. The solution is to wear and Alpha Layer on the classic body, which makes the classic body invisible.
System Clothes vs Mesh Clothes
The viewer’s built-in shirt, pants, underwear, and other layers are called System or Classic Clothes. In inventory, they have unique icons denoting shirts, pants, etc. They are for the Classic body. These are all hidden by a mesh body or clothes and the alpha layer.
A skin can be made for the Classic avatar as a System skin using GIMP/Photoshop and the built-in viewer tools. These are pretty much decals stuck on the Classic avatar body.
When you wear a fitted mesh body you need an Applier, a HUD, to ‘apply’ the skin to the fitted mesh body attachment. So, using GIMP/Photoshop and an Applier you can make a skin or clothes for a mesh body. There are no built-in viewer tools to make those skins and clothes.
In inventory these ‘mesh’ items are all represented by the cube icon used for objects, basically, user made things.
Fitted Mesh clothes do not have to have the same form as the body. They are not a decal. They are an attachment with a unique form. These clothes can often be worn with a Classic body, but usually fit poorly. To get a good-mesh-clothes-fit on a classic body one uses the standard sizes for clothes and avatar.
Because of the rate mesh changes in regard to the Appearance Shape Sliders, it is common for clothes to be made for a specific brand of mesh bodies. Most clothes are sold with multiple versions for different bodies. Wearing clothes made for a Maitreya body on a Slink body doesn’t work well.
For different activities in SL, people prefer different avatars, Classic or Mesh.
For various reasons, people mixed Classic and Mesh. For a time, I wore a Classic head and body with mesh hands and feet. Then I moved to add a mesh body I liked, with mesh hands and feet. I’ve kept my Classic head. But, I am looking at Mesh Heads. I changed to a mesh body to have a big choice of clothes and to look better.
I have outfits for Classic and Mesh bodies. I tend to prefer Mesh bodes and clothes these days. I am slowly throwing away my classic outfits.
In 2016 the Classic avatar built into the viewer changed. Linden Lab places a high priority on maintaining legacy compatibility. So, changes are somewhat restricted. However, Bento adds to the Classic avatar while retaining all the parts of the previous avatar.
Bento added bones to allow us to animate more of the avatar body. Prior to Bento fingers could not be animated. Nor could faces. All Classic facial expressions are built into the viewer. The built-in expressions (morphs) are not the same type of animation possible with Bento.
Bento allows us to add wings, tail, head, and ears that we can animate. We are no longer restricted to the built-in expressions.
So, fitted mesh built to use the new Bento bones is labeled ‘Bento’. So, heads and hands are the current big upgrades to appearance (2017).