Virtual Character Definition and Animation within the MPEG-4 Standard - 3D Modeling and Animation: Synthesis and Analysis Techniques for the Human Body - page 59

Figure 13. M ESH G RID representation of a humanoid model.

(b) CW

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+

(d) hierarchical mesh

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S W S V

S U

(a) M ESH G RID humanoid (c) RG (e) hierarchical reference system

can be used to render the object at the appropriate level of detail, can be obtained
from the connectivity-wireframe. The reference-grid is the result of a hierarchi-
cal reference system as shown in Figure 13e.
Starting from the humanoid model of Figure 13a, the following sections will
discuss the design particularities of the connectivity-wireframe, reference-grid,
and their relationship, such that the model can be animated using a hierarchical
skeleton-based approach.

The components of the M ESH G RID model: RG and CW
The original surface of the humanoid model has been designed by means of
implicit functions. A typical way to obtain a M ESH G RID object from such an
implicit surface definition is to apply a method called T RI S CAN (Salomie, 2002a),
which performs the contouring of the surface of the object at specified scanning
positions. The scanning positions are defined by the reference system specified
for the object.