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> instances 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 through
a distinct link object. The various subclasses provide the following
different mechanisms for organizing <DRM Geometry Representation>
instances:
- alternate hierarchy:
Each branch is a <DRM Geometry Hierarchy> component through a different
<DRM Hierarchy Data> link object, representing a different way of
organizing the same underlying collection of
<DRM Geometry Representation> instances.
- animation:
Each branch is a <DRM Geometry Hierarchy> component representing
a different frame in an animation sequence. This organizing principle
has no counterpart in the <DRM Aggregate Feature> class.
- classification:
Each branch is a <DRM Geometry Hierarchy> component through a different
<DRM Classification Data> link object, representing either a
different thematic layer, or a different classification of
<DRM Geometry Representation> instances
(e.g., roads, railroads) within a single thematic layer.
- continuous level of detail:
Each branch is either a <DRM Union Of Primitive Geometry>
component (usually a collection of
<DRM Polygon> instances), or a set of
<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
in the <DRM Aggregate Feature> class.
- level of detail:
Each branch is a <DRM Geometry Hierarchy> component through a
different (but possibly overlapping)
<DRM Base LOD Data> link object, representing
an alternative that shall be used at a specified level of detail.
- octant:
The <DRM Aggregate Geometry> instance
represents an octant-related organization, in which each branch is a
<DRM Geometry Hierarchy> component representing
an octant as identified through its <DRM Octant Data> link object.
- perimeter:
Each branch is a <DRM Geometry Hierarchy> component that is
located within a different cell of an irregular spatial index, as
defined through its <DRM Perimeter Data> link object.
- quadrant:
The <DRM Aggregate Geometry> instance represents
a quadrant related organization, in which each branch is a
<DRM Geometry Hierarchy> component
representing a quadrant, as identified through
its <DRM Quadrant Data> link object.
- separating plane:
Each branch is a <DRM Separating Plane Relations> component. Each
<DRM Separating Plane Relations> component
specifies a <DRM Separating Plane> component
P and up to two <DRM Geometry Hierarchy> components
each representing the data on either the positive or the negative side of
P as indicated through the corresponding
<DRM Separating Plane Data> link object.
This organizing principle has no counterpart in the
<DRM Aggregate Feature> class.
- spatial index:
The <DRM Aggregate Geometry> instance represents
a regularly spaced spatial index grid, in which each branch is a
<DRM Geometry Hierarchy> component
representing a different cell within the spatial index.
- state:
The <DRM Aggregate Geometry> instance
represents an environmental object that can take on different state
values for a specified EAC (the
state_tag,
which shall have the “state related” property).
Each branch is a <DRM Geometry Hierarchy>
component through a different <DRM State Data>
link object, representing an alternative that shall be
used to represent the
<DRM Aggregate Geometry> instance
when it takes on the specified state value.
- time:
The <DRM Aggregate Geometry> instance
represents an environmental object that has different
representations for different time periods. Each branch
is a <DRM Geometry Hierarchy> component
through a distinct (though possibly overlapping)
<DRM Time Constraints Data> link object,
representing an alternative that shall be used for the time period
specified through its
<DRM Time Constraints Data> link object.
- union of geometry hierarchy:
Each branch is a <DRM Geometry Hierarchy>
component. The reason for organizing them into separate components
is only minimally specified.
The counterpart of this mechanism among the subclasses of
<DRM Aggregate Feature> is the <DRM Union Of Features> class.
- union of primitive geometry:
Each branch is a <DRM Primitive Geometry> component;
<DRM Primitive Geometry> instances can be included in a transmittal
only as components of <DRM Union Of Primitive Geometry>
instances. The counterpart of this mechanism among the subclasses of
<DRM Aggregate Feature> is the <DRM Union Of Features> class.
If the value of the
unique_descendants
field is TRUE, each
descendant of this aggregation, that is, each
<DRM Geometry Representation>
instance that exists in the component tree
rooted at the <DRM Aggregate Geometry>
instance 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 Representation> instance
appears in more than one branch of the aggregation.
If the value of the
strict_organizing_principle
field 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.
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Class diagram
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Figure 6.4 —
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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Default field values
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Default field values for DRM_Aggregate_Geometry
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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 through the use of a <DRM Hierarchy Data> link object
- zero or more <DRM Animation Related Geometry> instances
- zero or more <DRM Classification Related Geometry> instances, each through the use of a <DRM Classification Data> link object
- zero or one <DRM Environment Root> instance
- zero or one <DRM Geometry Model> instance
- zero or more <DRM LOD Related Geometry> instances, each through the use of a <DRM Base LOD Data> link object
- zero or more <DRM Octant Related Geometry> instances, each through the use of a <DRM Octant Data> link object
- zero or more <DRM Perimeter Related Geometry> instances, each through the use of a <DRM Perimeter Data> link object
- zero or more <DRM Quadrant Related Geometry> instances, each through the use of a <DRM Quadrant Data> link object
- zero or more <DRM Separating Plane Relations> instances, each through the use of a <DRM Separating Plane Data> link object
- zero or more <DRM Spatial Index Related Geometry> instances, each through the use of a <DRM Spatial Index Data> link object
- zero or more <DRM State Related Geometry> instances, each through the use of a <DRM State Data> link object
- zero or more <DRM Time Related Geometry> instances, each through the use of 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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1An association between a
<DRM Feature Representation>
instance and a
<DRM Geometry Hierarchy> instance
indicates that the environmental object(s) that they
represent have the semantic relationship indicated by
the <DRM Base Association Data>
link object on the association relationship.
2An association between two
<DRM Geometry Hierarchy> instances
indicates that the environmental object(s) that they
represent have the semantic relationship indicated by
the <DRM Base Association Data>
link object on the association relationship.
3An association between a
<DRM Feature Representation>
instance and a
<DRM Geometry Hierarchy> instance
indicates that the environmental object(s) that they
represent have the semantic relationship indicated by
the <DRM Base Association Data>
link object on the association relationship.
4An association between two
<DRM Geometry Hierarchy> instances
indicates that the environmental object(s) that they
represent have the semantic relationship indicated by
the <DRM Base Association Data>
link object on the association relationship.
5An association from a
<DRM Hierarchy Summary Item>
instance to a <DRM Geometry Hierarchy>
instance indicates that the
<DRM Hierarchy Summary Item> instance
summarizes that <DRM Geometry Hierarchy>
instance.
6An association from a
<DRM Reference Surface> instance to a
<DRM Geometry Hierarchy> instance indicates
that the <DRM Geometry Hierarchy>
instance organizes the geometric objects that specify
the reference surface geometry of the
<DRM Reference Surface> instance.
7In the case where multiple
<DRM Collision Volume> components are
specified for the
<DRM Aggregate Geometry> instance,
the union
of the volumes thus specified is used in collision detection.
8A <DRM Aggregate Geometry> instance can have
a <DRM LSR Transformation> component only when the
<DRM Aggregate Geometry> instance is within
the scope of an LSR 3D SRF.
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Example(s)
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-
See concrete subclasses for examples.
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