Design patterns for HAnimHumanoid presenting skin and apparel
                         using HAnim2 standard in X3D4

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1. *Simple Skeleton*. skeleton field, simple skeleton structure, invisible or
    visualized by rendered ball-and-stick for joints, segments, sites.

2. *Simple Skeleton Mesh*. skeleton field, Shape geometry attached to segments,
   moving with skeleton but rendering is crude since no deformation occurs
   during animation if overlapping.

3. *Skin, Indexed Geometry only*. skin field, indexed Coordinate mesh with
   skinCoordIndex and weight connections at each of joint nodes for browser
   performance of smooth deformation when moving.

4. *Skin, Shape holding indexed geometry*. Allow skin field to hold Shape
   containing Appearance with Material or texture, similarly holding indexed
   mesh with skinCoordIndex connections at joints for smooth deformation 
   when moving. (Specification revision pending, Mantis 1408).

5. *Group, Transform, Switch, or LOD*. Similarly allow skin field to hold 
   Group or Transform-scaled collection of geometry, Switch, or LOD, then 
   one or more Shape nodes holding the combined indexed mesh.  Once again, 
   HAnim specification requirements holding identical indexed mesh with 
   skinCoord, skinCoordIndex connections for joints allows smooth deformation.
   Thus geometric mesh morphology is unchanged, only Color Appearance Material
   and Texture can vary among the different skin shapes.

6. *Synthesis*. Extra-large Coordinate mesh using duplicate points for 
   inner-volume (flesh mesh) and outer-volume (apparel mesh) geometry.  
   Likely possible with existing X3D4 specification but requires complex
   preprocessing of humanoid geometry.  Applying cloth physics likely not
   practical or possible.

7. *Apparel*. Future mainstreaming: add apparel field to future specification
   versions (namely HAnim2.1 and X3D4.1), allowing separate definition of 
   clothing that is independent of skin mesh.  Likely want an MFNode array 
   (rather than Group or Switch) to directly define multiple clothing layers.
   Likely need to consider special cases for cloth physics.

8. *Anatomy*.  Similar to apparel field: multiple epithelial tissue layers
   for surfaces of human organs are common, often with similar construction
   about concentric center-line spine through deformable organ.  This suggests
   that an adapted Extrusion node may be more relevant than meshes.  Likely 
   will also need to consider special cases for organ physics.  Note that this
   is similar (possibly identical) rationale to preceding analysis of apparel.

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Document online at
* https://www.web3d.org/x3d/content/examples/HumanoidAnimation/Skin/DesignPatternsApparelVariations.txt

Design-pattern template X3D model illustrating these patterns at
* https://www.web3d.org/x3d/content/examples/HumanoidAnimation/Skin/DesignPatternsApparelMedicalSkinLayersIndex.html

X3D4 Draft International Specification (DIS) refinements maintained at
* Mantis 1410: HAnimHumanoid skin definitions need to assign textures via Shape, Group, Switch etc.
* https://www.web3d.org/member-only/mantis/view.php?id=1410