The SEDRIS Data Representation Model
APPENDIX A - Classes
Geometry Model

Class Name: Geometry Model

Superclass - <SEDRIS Abstract Base>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class specifies a reusable representation of the geometry aspects of an environmental object represented by its <Model> aggregate.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

  1. The <Geometry Model> instance represents the hull of a tank.

  2. Consider a <Model> instance M, specified in an LSR 3D SRF, representing a missile and specifying a geometric representation. M is a component of a <Model Library> instance containing many <Model> instances representing missiles, each of which for consistency is expected to be specified in the same LSR 3D SRF and oriented pointing down the positive V axis.

    In the case of M, however, the <Geometry Model> component was provided by a data provider who uses the desired LSR 3D SRF, but for whom it is customary to specify missiles pointing down the -W axis. To make M consistent with the rest of the <Model Library> instance in which it resides, the <Geometry Model> component of M has an <LSR Transformation> component to reorient it to point down the positive V axis.

  3. A <Geometry Model> instance may be as large and complex as a large terrain model, or as simple as a single polygon at the lowest level of detail for some environmental object.

FAQs

Why does the <Geometry Model> class have <LSR Transformation> as a formal component? Isn't this taken care of by the formal <Transformation> component of the <Geometry Model Instance> class?

The <Geometry Model> class has a formal <LSR Transformation> component to allow all <Model> components of a <Model Library> instance to be given a uniform orientation. (Note that a data provider is not required to give them all a uniform orientation.)

Constraints

Associated by (one-way)

Composed of (two-way)

Composed of (two-way metadata)

Component of (two-way)

Inherited Field Elements

This class has no inherited field elements.

Notes

Associated from Notes


Geometry_Model_Instance

An association from a <Geometry Model Instance> instance to a <Geometry Model> instance indicates that the <Geometry Model Instance> instance references that particular <Geometry Model> instance.

Composed of Notes


Contact_Point

The <Contact Point> components allow explicit definition of where the <Model> instance contacts the surface on which it rests.


Geometry_Hierarchy

The <Geometry Hierarchy> component is actually required unless an empty <Model> instance is being created (see <<Non Empty Model Instance>>).


LSR_Transformation

The <LSR Transformation> component allows a data provider to specify a uniform model orientation within a <Model Library> instance although a data provider is not required to do so.


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Last updated: July 26, 2006 Copyright © 2006 SEDRIS