# .skeleton.blk

## Purpose of .skeleton.blk

Composite models are constructed from multiple dynamic models that share a
common skeleton. Below are the rules for creating a `.skeleton.blk` file for a
composite model.

## Examples

Let's break down the configuration using the example of a tank with various
turret and gun options.

```
name:t="tank_body.lod00.dag"
attachSubSkel{
  attach_to:t="bone_turret"
  skel_file:t="turret_a.lod00.dag"
  skel_node:t="bone_turret"
  attachSubSkel{
    attach_to:t="bone_gun_a"
    skel_file:t="gun_a.lod00.dag"
    skel_node:t="bone_gun_a"
  }
  attachSubSkel{
    attach_to:t="bone_gun_b"
    skel_file:t="gun_b.lod00.dag"
    skel_node:t="bone_gun_b"
    add_prefix:t="G1:"
  }
  attachSubSkel{
    attach_to:t="bone_gun_c"
    skel_file:t="gun_b.lod00.dag"
    skel_node:t="bone_gun_b"
    add_prefix:t="G2:"
  }
}
attachSubSkel{
  attach_to:t="bone_turret"
  skel_file:t="turret_b.lod00.dag"
  skel_node:t="bone_turret"
  add_prefix:t="T1:"
}
```

### Parameter Details

- `name:t=`: The name of the parent model.
- `attachSubSkel`: Block for adding a dynamic model.
  - `attach_to:t=`: Node in the parent skeleton to which the dynamic model is
    linked.
  - `skel_file:t=`: Name of the child model.
  - `skel_node:t=`: Node in the child skeleton that links to the parent
    skeleton.
  - `add_prefix:t=`: Prefix for all nodes of the child model.

### Explanation

In the `.skeleton.blk` example above, we add the `turret_a` and `turret_b`
models to the skeleton generated by `tank_body`, linking them to the
`bone_turret`. Additionally, we attach the guns `gun_a` and `gun_b` to the nodes
`bone_gun_a`, `bone_gun_b`, and `bone_gun_c` of `turret_a`, with `gun_b` being
linked twice to different bones.

Since we are creating a single common skeleton, there cannot be nodes with
identical names. To address this, we assign a unique prefix to the nodes of each
duplicate. For instance, the nodes of the two copies of `bone_gun_b` receive the
prefixes `G1` and `G2`, while the nodes of `turret_b` receive the prefix `T1`.

```{important}
- When specifying the attachment node, do not account for the automatically
  added prefixes.
- If a child node is linked to a node with the same name, the previous node is
removed from the hierarchy to avoid duplicates.
```

### Hierarchical Dependencies

While it's possible to create long chains of dependencies, simpler structures
are easier to manage. Before adding another level, ensure its necessity.

A multi-level hierarchy might look like this:

```
name:t="papa.lod00.dag"
attachSubSkel{
  attach_to:t="bone_papa"
  skel_file:t="child.lod00.dag"
  skel_node:t="bone_child"
  add_prefix:t="layer01:"
  attachSubSkel{
    attach_to:t="bone_child"
    skel_file:t="child.lod00.dag"
    skel_node:t="bone_child"
    add_prefix:t="layer02:"
    attachSubSkel{
      attach_to:t="bone_child"
      skel_file:t="child.lod00.dag"
      skel_node:t="bone_child"
      add_prefix:t="layer03:"
      attachSubSkel{
        attach_to:t="bone_child"
        skel_file:t="child.lod00.dag"
        skel_node:t="bone_child"
        add_prefix:t="layer04:"
      }
    }
  }
}
```

This structure allows for extensive customization while maintaining
manageability by using prefixes to avoid naming conflicts and ensure proper
hierarchy.