(proportional to speed)
Spring
Gravity
Wind
Motion Designer (MD) reshapes objects according to wind, gravity, and the object's own motions by using elastic body models to create animation data. Its calculation models are described below.
Elastic body models
A polygon object normally includes points, polygons, and surfaces. In MD, these are expanded as follows:
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| Point (a location in 3D space) |
A point with gravity and air resistance (proportional to speed) |
| Polygon (information for connecting points) | Each line constituting a polygon is regarded as a spring and exerts power over points. |
| Surface (polygon attributes) | Parameters needed for an elastic body model are added. |
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Spring Gravity Wind |
For this expanded polygon object (= elastic body model), the point location, the speed, and the spring force are calculated for every minute duration in order to reproduce its motions.
Hold-Structures
Since a pure elastic body model simulates only the surface
structure, only two-dimensional motions, such as of cloth, can
be handled. In order to simulate elastic 3D motions, such
as of Tofu, a hold-structure should be incorporated. As a hold-structure,
a spring
is set up between each point (in motion) and its original position
to sustain the original shape of the object.
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Sub-Structures
The surface of a pure, elastic body model has a high degree of freedom and is subject to distortion which does not occur on real objects. To prevent this, an auxiliary spring structure should be created, apart from a polygon, to restrict the instability of the surface. This substructure can improve a two dimensional model (with no thickness) into a model having some thickness. However, this substructure requires "reinforcement" by using a large number of spring structures depending on the structure of the polygon. Note that such substructures might adversely affect the speed of calculation.
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