Level Of Detail Related Geometry

The SEDRIS Data Representation Model APPENDIX A - Classes Level Of Detail Related Geometry

Class Name: Level Of Detail Related Geometry

Superclass - <Aggregate Geometry>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class is an aggregation of <Geometry Hierarchy> objects in which each component <Geometry Hierarchy> is an alternate representation of the same entity at a different level of detail. Each component < Geometry Hierarchy> is a collection of <Geometry> objects with a different, possibly overlapping, <Base Level Of Detail Data> value, representing alternatives that should be used at different viewing ranges, map scales, spatial resolution, and so on.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

This class appears on only one page of the DRM class diagram.

Example

Consider a <Model> of a house, organized based on viewing ranges. If the viewer is farther away than 1000 metres, the house is not visible. From 500 metres to 1000 metres, the roof and walls are visible but not in great detail. From 0 metres to 500 metres, the windows and door become visible. Consequently, the <Model> is visible at 2 distance-related levels of detail: 0-500 metres, and 500-100 metres.

For the more detailed 0.0 - 500.0 metres, different "wall" <Models> are instanced for the walls containing the windows and doors; otherwise, the structure of the two levels, for this example, is similar.

Three <Models> of a given building are created, each with different <Polygon> counts. The most accurate representation is useful up to a viewing distance of 1 kilometre, the second from 1 kilometre to 2 kilometres, and the third for 2 kilometres to 5 kilometres.

To indicate this, a 4th <Model> can be created as follows:

              <Model>
                <>
                   |
           <Geometry Model>
                <>
                   |
    <Level Of Detail Related Geometry>
                <>
    ---------------------------------------------------
    |                        |                        |
    |--<Distance LOD Data>   |--<Distance LOD Data>   |--<Distance LOD Data>
    |  0.0 - 1.0             |    1.0 - 2.0           |  2.0 - 5.0
    |                        |                        |
<GMI>              <GMI>              <GMI>

FAQs

No FAQs supplied.

Constraints

Associated by (one-way)(inherited)

zero or one <Hierarchy Summary Item> instance (notes)
zero or more <Reference Surface> instances (notes)

Associated with (two-way)(inherited)

zero or more <Feature> instances (notes)
zero or more <Geometry Hierarchy> instances (notes)

Composed of (two-way)(inherited)

zero or more {ordered} <Attribute Set Index> instances
zero or one <Classification Data> instance
zero or more <Property Table> instances
zero or more <Property Table Reference> instances
zero or more <Property Value> instances
zero or one <Reference Surface> instance
zero or more <Sound Instance> instances
zero or more <Base Level Of Detail Data> instances
zero or one <Bounding Volume> instance
zero or one <Centre Of Buoyancy> instance
zero or one <Centre Of Mass> instance
zero or one <Centre Of Pressure> instance
zero or more <Collision Volume> instances (notes)
zero or more <Colour> instances
zero or one <Conformal Behaviour> instance
zero or more <Geometry Topology Hierarchy> instances
zero or more <Hierarchical Table> instances
zero or more {ordered} <Image Mapping Function> instances
zero or one <Light Rendering Properties> instance
zero or more <Light Source> instances
zero or one <LSR Transformation> instance
zero or one <Overload Priority Index> instance
zero or one <Perimeter Data> instance
zero or one <Presentation Domain> instance
zero or more <Property Description> instances
zero or one <Rendering Priority Level> instance
zero or one <Rendering Properties> instance
zero or one <Spatial Domain> instance
zero or one <Stamp Behaviour> instance

Composed of (two-way)

one or more <Geometry Hierarchy> instances through <Base Level Of Detail Data>

Composed of (two-way metadata)(inherited)

zero or one <Time Constraints Data> instance
zero or one <Access> instance
zero or more <Browse Media> instances
zero or more <Cross Reference> instances
zero or one <Data Quality> instance
zero or one <Keywords> instance
zero or one <Point Of Contact> instance

Component of (two-way)(inherited)

zero or more <Alternate Hierarchy Related Geometry> instances through <Hierarchy Data>
zero or more <Animation Related Geometry> instances
zero or more <Classification Related Geometry> instances through <Classification Data>
zero or one <Environment Root> instance
zero or one <Geometry Model> instance
zero or more <Level Of Detail Related Geometry> instances through <Base Level Of Detail Data>
zero or more <Oct Tree Related Geometry> instances through <Oct Tree Data>
zero or more <Perimeter Related Geometry> instances through <Perimeter Data>
zero or more <Quad Tree Related Geometry> instances through <Quad Tree Data>
zero or more <Separating Plane Relations> instances through <Separating Plane Data>
zero or more <Spatial Index Related Geometry> instances through <Spatial Index Data>
zero or more <State Related Geometry> instances through <State Data>
zero or more <Time Related Geometry> instances through <Time Constraints Data>
zero or more <Union Of Geometry Hierarchy> instances

Inherited Field Elements

SE_Boolean	unique_descendants;	(notes)
SE_Boolean	strict_organizing_principle;	(notes)

Field Elements

SE_LOD_Data_Type	lod_data_type;

Notes

Associated with Notes

Feature

 An association between a <Geometry Hierarchy> instance and a
 <Feature> instance indicates that the <Geometry Hierarchy>
 and the <Feature> are alternate representations of the same
 environmental object.

Geometry_Hierarchy

 An association between two <Geometry Hierarchy> instances
 indicates that they are alternate representations of the same
 environmental object.

Hierarchy_Summary_Item

 An association from a <Hierarchy Summary Item> instance to a
 <Geometry Hierarchy> indicates that the <Hierarchy Summary Item>
 summarizes that <Geometry Hierarchy>.

Reference_Surface

 An association from a <Reference Surface> instance to a
 <Geometry Hierarchy> indicates that the <Geometry Hierarchy>
 organizes the geometric objects that specify the resolution
 surface of the <Reference Surface>.

Composed of Notes

Collision_Volume

 In the case where multiple <Collision Volume> components are
 specified for a given <Aggregate Geometry>, the union of the
 volumes thus specified is used in collision detection.

Fields Notes

unique_descendants

 If this value is SE_TRUE, each 'descendant' of this aggregation -
 that is, each <Geometry> object that exists in the component tree
 rooted at the given <Aggregate Geometry> - shall be unique, in the
 sense that it shall appear in only one 'branch' of this aggregation.
 If unique_descendants is SE_FALSE, at least one <Geometry> object
 appears in more than one 'branch' of the aggregation.

strict_organizing_principle

 If this value is SE_TRUE, each 'branch' of this aggregation
 strictly complies with the organizing principle for its
 particular subclass. If this value is SE_FALSE, at least
 one 'branch' does not strictly comply with the given
 organizing principle. See the organizing principle constraint
 for each specific subclass for details.

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Last updated: October 1, 2002