Layered Construction

Layered construction is an avatar construction technique in which the avatars are built up as multiple concentric layers using different modelling techniques.

Tthe bones are placed for animation first, rather than last as in traditional avatar construction. A rigid skeleton with hinge and ball joints is placed on top of the animation bones. The animation bones are not typically modelled as visible models, so this marks a profound change from the standard approach. They are not usually modelled accurately, but placed in functional form only.

On top of the bones, comes an internal layer, sort-of like the organs of the avatar. Like the bones, it is not modelled as an attempt to put the organs in, but is purely functional as support for the next layer. It may be texturemapped, but rarely is, unless the avatar is likely to be sliced open at some point during interaction. It is a traditional polygonal mesh layer, using the bones as a guide for placement. It is there mainly to ensure the next layer hangs in the right places, and to ensure the joints are covered properly.

The third layer consists entirely of deformable shapes anchored to the organ-layer. Oftewn metaballs are used to convey the proper organic feeling, but metaballs don't perform well near complex, intricate joints such as with the fingers and toes, or wit hthe complex expression of the face, so other deformable shapes are often employed for these locations. The purpose of the third layer is to give a realistic skin-like look and feel as the avatar moves around. It is extremely computationally expensivre, and so rarely employed for real-time interaction at the current time, but produces by far the best visual and tactile results.

A fourth layer is often added on top of the deformable shapes, using more deformable shapes, serving as cloth. These clothes also use their own internal 'organ' layer to keep everything properly positioned, and serve to constrain the fleshy metaball 'skin' of the avatar, forcing it into relistic forms as you would expect from a clothed person.

See Also: Metaball, Metaball Modelling, Deformable Shape, Avatar, Bone Inverse Kinematics, Bone Level Of Detail, Bone Weighting, Hierarchical Skeletal Modelling System

Below, we offer a selection of links from our resource databases which may match this term.

Layered Construction

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Kluge: The Haphazard Construction of the Human Mind

The human brain is the ultimate legacy system, with bodges, klonks, workarounds and kludges forcing it to work as a (mostly) cohesive system.

Project Gerhome
The project, a French initiative, run by the French centre for construction research (CSTB), is designed as telehealth for the elderly. Homes are tripped out with sensors and computer systems that monitor the health and behaviour of the individual, and alert a central depot should anything outside of normal routine occur.

Large Image Display: AI: Artificial Intelligence: Facial Access Panel
This robot girl - gynoid - is used as a demonstration model by the film "AI: Artificial Intelligence", to show several aspects of their take on robot behaviour and construction. In this still, the gynoid's face is sliding apart for maintenance. This is not particularly realistic, for several reasons.

Large Image Display: Animatrix: Beyond: Arriving On Scene
Whilst it is true that an administration vehicle in a heavily natural laws based VR would have to obey those physical laws or risk damage to the simulation wherever it traveled, it is also true that it can bend the rules to a degree. An invincible construction material is impossible within those laws, but a fantastic material that can absorb almost every blow, and can smash through a wall at 70mph, without taking a dent, is theoretically not impossible. That's good enough to avoid breaking the rules.

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