AIM@SHAPE Glossary

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 Subdivision

The strategy often used in CAGD is to divide the geometric elements describing the problem into pieces. The idea behind subdivision is that the problem gets simpler when addressing sub pieces of the original geometry. In many cases this is true. However, if care is not taken and the subdivision is not performed in the proper location, the sub-problems can get more complicated than the original problem. Subdivision algorithms play a central role in a number of algorithms in CAD:

- Visualization algorithms to produce an accurate triangulation of surfaces for display;
- Intersection algorithms for potentially simplifying the intersection problem.

 Skeleton

(1) In algebraic topology, a p -skeleton is a simplicial sub-complex of a simplicial complex K that is the collection of all simplices of K of dimension at most p .
(2) Related with the notion of medial axis, the skeleton of a bounded open subset X is the set of centres of maximal balls, where an open ball B is maximal if every ball that contains B and is contained in X equals B .
(3) The skeleton of a shape is the reduced object representation that conforms to human visual perception and preserve the salient shape features.
(4) Implicit skeleton: i n the field of implicit modelling, it is used for a set of geometric primitives to which a distance can be computed. These primitives are used for generating the field function that defines the surface. Skeleton-based implicit modelling can also be referred to as “Structural Implicit Modelling”, since the skeleton defines an internal structure for the model.

 Sensor

(1) An electronic device used to measure a physical quantity such as temperature, pressure or loudness and convert it into an electronic signal of some kind (e. g. a voltage).
Sensors can be classified in passive (not interacting with the scene) and active (interacting with the scene). Sensors are normally components of some larger electronic system such as a computer control and/or measurement system.
(2) Virtual entities that give to Virtual Humans the possibility to acquire information (stimuli) coming from their surrounding virtual environment. Virtual sensors let a VH see, hear and touch its virtual environment and react in consequence. The information acquired is then analyzed with different algorithms and/or Behavior Controllers that produce animation as output (the VH reacts to stimuli).