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The SEDRIS Data Representation Model
APPENDIX A - Classes Geometry Model Instance |
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An instance of this DRM class specifies a single use of a <Geometry Model> instance within a given transmittal, including variations or specialization unique to that case. In particular, a <Geometry Model Instance> instance is used to transform a <Geometry Model> instance into the SRF of another <Geometry Model> instance or that of an <Environment Root> instance.
Consider a <Model> instance representing a building consisting of a <Geometry Model> component describing its geometric representation, where the <Model> instance is specified in an LSR 3D SRF.
To instantiate this <Model> instance in an <Environment Root> instance which specifies a Celestiodetic 3D SRF, the data provider constructs a <Geometry Model Instance> instance with a <World Transformation> component, and incorporates it into the <Geometry Hierarchy> component of that <Environment Root> instance. The <World Transformation> instance specifies the <CD 3D Location> instance to which the origin of the <Model> instance is mapped, together with any other transformation information required to orient and scale the <Model> instance properly.
Consider a <Geometry Model> instance R describing the rotor of a helicopter, and intended for use within a larger <Geometry Model> instance of the entire helicopter. Both are specified in 3D LSR SRFs.
The helicopter model contains a <Geometry Model Instance> instance of R, with an <LSR Transformation> component L containing a <Rotation> instance with a <Rotation Control Link> component. L specifies both the transformation required to position the rotor within the helicopter model, and the <Variable> instance within the larger helicopter <Model> instance that is plugged into the internal <Variable> instance of R for angle of rotation.
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