## The AIM@SHAPE Glossary

### Alphabetical list of terms

- half-edge data structure
- A data structure for encoding a mesh. For each edge of the mesh, the data structure stores two half-edges, and information about the edge is split between such two halves. Each half-edge stores the index of its origin, the index of the face on its left, two indices of its previous and next edges along the boundary of that face, and the index of its twin half-edge, which is oriented in the opposite direction. Information attached to vertices and faces are the same as in the winged-edge and in the DCEL data structures.
- hand posture
- Specification of joint values describing the hand posture required to grab or manipulate a Smart Object.
- h-anim skeleton
- The H-Anim skeleton is an animation-oriented structural descriptor. It is an efficient representation of an articulated skeleton for Virtual Humans. It was initially proposed by the Humanoid Animation Working Group (http://www.h-anim.org). Now it has been adopted by the MPEG-4 specification as one of the standard structural descriptors for animatable Humanoid Virtual Characters.
- haptic device
- A device which allows a user to interact with a computer by receiving tactile feed back. This feedback is achieved by applying a degree of opposing force to the user along the x, y, and z axes. There are two main types of haptic devices: glove or pen-type devices that allow the user to "touch" and manipulate 3-dimensional virtual objects and devices that allow users to "feel" textures of 2-dimensional objects with a pen or mouse-type interface.
- healing
- Technology to detect and repair connectivity problems (e.g. gaps) in order to have a conform geometric model.
- hedgehog diagram
- A hedgehog diagram (curvature profile) for planar curves visualizes the curve normals proportional to the curvature value at some curve points.
- hierarchical b-spline (h-spline)
- A scheme of defining surfaces using overlays of B-spline surfaces. A complex surface is defined as a single tensor product square patch with other tensor product patches laid on top of it at different orientations and sizes.
- hierarchical model
- Organisation of data records as a collection of trees, rather than arbitrary graphs. With respect to geometry a rough description of the geometry is located at the highest level, and more and more details are added descending the tree.
- highlight line
- A highlight line is defined as the locus of all points on a surface where the orthogonal distance between the surface normal and the light line is zero.
- homotopy type
- A class formed by sets in the Euclidean space which have essentially the same structure, regardless of size, shape and dimension. The essential structure is what a set keeps when it is transformed by compressing or dilating its parts, but without cutting or gluing.
- human joint
- Joint node, basic building block of a Virtual Human skeleton, representing the actual joints on a human being: shoulders, wrists, vertebrae, etc. A joint can have different kinds of children: they can be segments (typically used to store the actual geometry of each limb), or other joints. Under certain cases (not H-Anim 1.0 compliant) a joint could directly store a geometry node.
- human segment
- Node specialisation for H-Anim Segments, typically used as the container of a 3D shape representing a given human body part.

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