The SEDRIS Data Representation Model
APPENDIX A - Classes
Continuous Level Of Detail Related Geometry
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Class Name: Continuous Level Of Detail Related 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> 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).
The general idea is that basic <Polygon>
instances have fragmented <Polygon> instances
within them, and those <Polygon> instances may have
subsequent fragmentation.
Primary Page in DRM Diagram:
Secondary Pages in DRM Diagram:
This class appears on only one page of the DRM class diagram.
Example
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.
(NOTE that this example only shows two levels of polygon fragmentation.
Each
<Continuous Level Of Detail Related Geometry>
could contain component
<Continuous Level Of Detail 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 Level Of Detail Related Geometry> is not organized
with link class instances, such as
<Base Level Of Detail 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 by (one-way)(inherited)
Associated with (two-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)
Notes
Associated with Notes
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.
An association between two <Geometry Hierarchy> instances
indicates that they are alternate representations of the same
environmental object.
An association from a <Hierarchy Summary Item> instance to a
<Geometry Hierarchy> indicates that the <Hierarchy Summary Item>
summarizes that <Geometry Hierarchy>.
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
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
If this value is SE_TRUE, each 'descendant' of this aggregation -
that is, each <Geometry> 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> instance
appears in more than one 'branch' of the aggregation.
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.
This flag identifies if the current level is the lowest level of
fragmentation for a specific chain. Set to SE_TRUE if no other
<Continuous Level Of Detail> nodes are found below this chain's
current level.
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Next: Control Link.
Up:Index.
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Last updated: May 15, 2003
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Copyright © 2003 SEDRIS™
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