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Property
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Description
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Class
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Superclass
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Subclass
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Definition
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An instance of this DRM class specifies a collection of
<DRM Primitive Geometry> or
<DRM Geometry Hierarchy> instances, organized
according to some organizing principle specific to the particular
subclass of <DRM Aggregate Geometry>
being considered.
For most subclasses of <DRM Aggregate Geometry>,
each individual branch of the aggregation is explicitly identified by
a distinct link object. The various subclasses provide different
mechanisms for organizing <DRM Geometry> instances, which
include:
- ALTERNATE HIERARCHY:
Each branch is a <DRM Geometry Hierarchy>
with a different <DRM Hierarchy Data>
instance, representing a different way of organizing the same underlying
collection of <DRM Geometry> instances.
- ANIMATION:
Each branch is a <DRM Geometry Hierarchy>,
representing a different frame in an animation sequence. This
organizing principle has no counterpart on the
<DRM Feature> side.
- CLASSIFICATION:
Each branch is a <DRM Geometry Hierarchy>
with a different <DRM Classification Data>
instance, representing either a different thematic layer, or a different
classification of <DRM Geometry> instances
(e.g., roads, railroads) within a single thematic layer.
- CONTINUOUS_LEVEL_OF_DETAIL:
Each branch is either a <DRM
Union Of Primitive Geometry> (usually a collection of
<DRM Polygon> instances), or a set of fragmented
<DRM 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). This
mechanism is used to represent continuous terrain or
continuous adaptive terrain. This organizing principle has no counterpart
on the <DRM Feature> side.
- LEVEL_OF_DETAIL:
Each branch is a <DRM Geometry Hierarchy>
with a different (but possibly overlapping)
<DRM Base Level Of Detail Data>
instance, representing an
alternative that shall be used at a specified level of detail.
- OCTANT:
The <DRM Aggregate Geometry> represents
an octant, in which each branch is a <DRM
Geometry Hierarchy> representing an octant,
as identified by its <DRM Octant Data> instance.
- PERIMETER:
Each branch is a <DRM Geometry Hierarchy>
that is located within a different cell of an irregular spatial index, as
defined by its <DRM Perimeter Data> instance.
- QUADRANT:
The <DRM Aggregate Geometry> represents
a quadrant, in which each branch is a <DRM
Geometry Hierarchy> representing a quadrant,
as identified by its <DRM Quadrant Data>
instance.
- SEPARATING_PLANE:
Each branch is a <DRM
Separating Plane Relations>, each branch of which
is a <DRM Geometry Hierarchy>
instance that is on either the positive or negative side of the
associated <DRM Separating Plane>, as indicated
by the <DRM Separating Plane Data>
instance for that branch. This organizing principle has no
counterpart on the <DRM Feature> side.
- SPATIAL_INDEX:
The <DRM Aggregate Geometry> represents
a regularly spaced spatial index grid, in which each branch is a
<DRM Geometry Hierarchy> instance
representing a different cell within the spatial index.
- STATE:
The <DRM Aggregate Geometry> represents
something that can take on different state values for a specified
EDCS Attribute Code (the
state_tag, which shall have the “state-related” property).
Each branch is a <DRM Geometry Hierarchy>
instance with a different <DRM State Data>
instance, representing an alternative that shall be
used to represent the <DRM
Aggregate Geometry> when it takes on the
specified state value.
- TIME:
The <DRM Aggregate Geometry>
represents something that has different
representations for different time periods, so that each branch
is a <DRM Geometry Hierarchy>
instance with a distinct (though possibly overlapping)
<DRM Time Constraints Data>
instance, representing an
alternative that shall be used for the time period specified by
its <DRM Time Constraints Data>.
- UNION_OF_GEOMETRY_HIERARCHY:
Each branch is a
<DRM Geometry Hierarchy>
instance. The reason for organizing them into separate components
is only minimally specified.
This mechanism's counterpart on the <DRM Feature>
side is <DRM Union Of Features>.
- UNION_OF_PRIMITIVE_GEOMETRY:
Each branch is a
<DRM Primitive Geometry>
instance; <DRM Primitive Geometry>
can be included in a transmittal only by means of
<DRM Union Of Primitive Geometry>
instances.
This mechanism's counterpart on the <DRM Feature>
side is <DRM Union Of Features>.
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Class diagram
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Figure 6.7 —
DRM_Aggregate_Geometry
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Inherited field elements
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Field name
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Range
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Field data type
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None |
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Field elements
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Associated to (one-way) (inherited) |
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Associated to (one-way) |
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Associated by (one-way) (inherited) |
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Associated by (one-way) |
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Associated with (two-way) (inherited) |
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Associated with (two-way) |
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Composed of (two-way) (inherited) |
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Composed of (two-way) |
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Composed of (two-way metadata) (inherited) |
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Composed of (two-way metadata) |
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Component of (two-way) (inherited) |
- zero or more <DRM Alternate Hierarchy Related Geometry> instances, each with a <DRM Hierarchy Data> link object
- zero or more <DRM Animation Related Geometry> instances
- zero or more <DRM Classification Related Geometry> instances, each with a <DRM Classification Data> link object
- zero or one <DRM Environment Root> instance
- zero or one <DRM Geometry Model> instance
- zero or more <DRM Level Of Detail Related Geometry> instances, each with a <DRM Base Level Of Detail Data> link object
- zero or more <DRM Octant Related Geometry> instances, each with a <DRM Octant Data> link object
- zero or more <DRM Perimeter Related Geometry> instances, each with a <DRM Perimeter Data> link object
- zero or more <DRM Quadrant Related Geometry> instances, each with a <DRM Quadrant Data> link object
- zero or more <DRM Separating Plane Relations> instances, each with a <DRM Separating Plane Data> link object
- zero or more <DRM Spatial Index Related Geometry> instances, each with a <DRM Spatial Index Data> link object
- zero or more <DRM State Related Geometry> instances, each with a <DRM State Data> link object
- zero or more <DRM Time Related Geometry> instances, each with a <DRM Time Constraints Data> link object
- zero or more <DRM Union Of Geometry Hierarchy> instances
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Component of (two-way) |
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Constraints
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Clarifications
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1
If this value is TRUE, each
“descendant” of this aggregation - that is, each
<DRM Geometry>
instance that exists in the component tree rooted
at the given <DRM Aggregate Geometry> -
shall be unique, in the sense that it shall appear in only one
“branch” of this aggregation. If
unique_descendants
is FALSE, at least one
<DRM Geometry> instance
appears in more than one “branch” of the aggregation.
2
If this value is TRUE, each
“branch” of this aggregation
strictly complies with the organizing principle for its
particular subclass. If this value is
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.
3
An association between a
<DRM Geometry Hierarchy> instance
and a <DRM Feature> instance indicates that
the <DRM Geometry Hierarchy>
and the <DRM Feature> are
alternate representations of the same
environmental object.
4
An association between two
<DRM Geometry Hierarchy> instances
indicates that they are alternate representations of the same
environmental object.
5
An association from a
<DRM Hierarchy Summary Item>
instance to a <DRM Geometry Hierarchy>
indicates that the
<DRM Hierarchy Summary Item>
summarizes that <DRM Geometry Hierarchy>.
6
An association from a
<DRM Reference Surface> instance to a
<DRM Geometry Hierarchy> indicates
that the <DRM Geometry Hierarchy>
organizes the geometric objects that specify the resolution
surface of the <DRM Reference Surface>.
7
In the case where multiple
<DRM Collision Volume> components are
specified for a given
<DRM Aggregate Geometry>, the union
of the volumes thus specified is used in collision detection.
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Example(s)
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See concrete subclasses for examples.
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