The SEDRIS Data Representation Model
APPENDIX A - Classes
Continuous LOD Related Geometry

Class Name: Continuous LOD Related Geometry

Superclass - <Aggregate Geometry>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class is used to represent continuous terrain or continuous adaptive terrain, by replacing a <Polygon> instance with a set of fragmented <Polygon> instances that represent the terrain at a finer level of detail at close range (or alternatively, with a coarser level of detail at long range).

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

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

Example

  1. A Continuous LOD node can be fragmented into one or more <Polygon> instances, and will then have zero or more Continuous LOD nodes as subnodes. Any Continuous LOD node that contains Continuous LOD nodes under it will have the terminating_node flag set to SE_FALSE. The <Union Of Primitive Geometry> node will contain <Polygon> data. If a Continuous LOD node is encountered with the terminating_node flag set to SE_TRUE, that means it only has a <Union Of Primitive Geometry> node under it.

    Continuous LOD Related Geometry, Example 1

    (NOTE that this example only shows two levels of polygon fragmentation. Each <Continuous LOD Related Geometry> could contain component <Continuous LOD Related Geometry> instances, but that would make a huge picture. Only the idea is represented here.)

FAQs

How can a consumer find the finest fragmentation of polygons?

Follow all Continuous LOD chains. Wherever a Continuous LOD node with terminating_node set to SE_TRUE is encountered, that identifies the finest fragmentation of <Polygon> instances under the <Union Of Primitive Geometry> at that Continuous LOD.

What do the "terminating" <Polygon> instances represent?

The combination of polygons from the Continuous LOD nodes with terminating_node set to SE_TRUE make up the <Polygon> identified under the <Union Of Primitive Geometry> from the Continuous LOD node with terminating_node set to SE_FALSE.

Since <Continuous LOD Related Geometry> is not organized with link class instances, such as <Base LOD Data>, how can consumers determine the range between fine and coarse data?

The uniqueness of Continuous LOD data is that it is not based on range data for an entire area to blend in. Rather, the blending of data is performed typically at the IG. In source data, all potential polygon fragmentations have been identified. Therefore, it is not necessary to have range data stored in a link class.

Constraints

Associated to (one-way) (inherited)

Associated by (one-way) (inherited)

Composed of (two-way) (inherited)

Composed of (two-way)

Composed of (two-way metadata) (inherited)

Component of (two-way) (inherited)

Component of (two-way)

Inherited Field Elements

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

Field Elements

SE_Boolean terminating_node; (notes)

Notes

Associated to Notes


Feature_Representation

 An association between a <Feature Representation> instance
 and a <Geometry Hierarchy> instance indicates that the
 environmental object(s) that they represent have the
 semantic relationship indicated by the <Base Association Data>
 instance on the association relationship.

Geometry_Hierarchy

 An association between two <Geometry Hierarchy> instances
 indicates that the environmental object(s) that they
 represent have the semantic relationship indicated by
 the <Base Association Data> instance on the association
 relationship.

Associated from Notes


Feature_Representation

 An association between a <Feature Representation> instance
 and a <Geometry Hierarchy> instance indicates that the
 environmental object(s) that they represent have the
 semantic relationship indicated by the <Base Association Data>
 instance on the association relationship.

Geometry_Hierarchy

 An association between two <Geometry Hierarchy> instances
 indicates that the environmental object(s) that they
 represent have the semantic relationship indicated by
 the <Base Association Data> instance on the association
 relationship.

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 the value of the unique_descendants field is SE_TRUE, each
 descendant of this aggregation,
 that is, each <Geometry Representation> instance 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 Representation> instance
 appears in more than one branch of the aggregation.

strict_organizing_principle

 If the value of the strict_organizing_principle field 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.

terminating_node

 The terminating_node field specifies whether the current level of
 fragmentation is the lowest level of fragmentation for a specific
 chain. This flag is set to SE_TRUE if no other
 <Continuous LOD Related Geometry> instances are
 found below this chain's current level.
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Last updated: July 16, 2004 Copyright © 2004 SEDRIS™