The Web3D H-Anim Standards

The Web3D H-anim working group (H-anim) was formed so that developers
could agree on a standard naming convention for human body parts and joints.
The human form has been studied for centuries and most of the parts alreadyhave medical (or Latin) names. This group has produced the Humanoid
Animation Specification (H-anim) standards, describing a standard way of
representing humanoids in VRML. These standards allow humanoids created
using authoring tools from one vendor to be animated using tools from another.
H-anim humanoids can be animated using keyframing, inverse kinematics,
performance animation systems and other techniques. The three main design
goals of H-anim standards are:
• Compatibility: Humanoids should be able to display/animate in any VRML
compliant browser.
• Flexibility: No assumptions are made about the types of applications that
will use humanoids.
• Simplicity: The specification should contain only what is absolutely necessary.
Up to now, three H-anim standards have been produced, following developments
in VRML standards, namely the H-anim 1.0, H-anim 2.0 and H-anim 2001
standards.
The H-anim 1.0 standard specified a standard way of representing humanoids in
VRML 2.0 format. The VRML Humanoid file contains a set of Joint nodes, each
defining the rotation center of a joint, which are arranged to form a hierarchy.
The most common implementation for a joint is a VRML Transform node, which
is used to define the relationship of each body segment to its immediate parent,
although more complex implementations can also be supported. Each Joint node
can contain other Joint nodes and may also contain a Segment node, which
contains information about the 3D geometry, color and texture of the body part
associated with that joint. Joint nodes may also contain hints for inversekinematics
systems that wish to control the H-anim figure, such as the upper and
lower joint limits, the orientation of the joint limits, and a stiffness/resistance
value. The file also contains a single Humanoid node, which stores humanreadable
data about the humanoid, such as author and copyright information. This
node also stores references to all the Joint and Segment nodes. Additional nodes
can be included in the file, such as Viewpoints, which may be used to display the
figure from several different perspectives.
The H-anim 1.1 standard has extended the previous version in order to specify
humanoids in the VRML97 standard (successor of VRML 2.0). New features
include Site nodes, which define specific locations relative to the segment, and
Displacer nodes that specify which vertices within the segment correspond to
a particular feature or configuration of vertices. Furthermore, a Displacer node
may contain “hints” as to the direction in which each vertex should move, namely