Class Name: Colour Index Control Link
Subclasses
This DRM class is concrete and has no subclasses.
Definition
An instance of this DRM class specifies
an <Expression> instance that determines the
index field value and/or
an <Expression> instance that determines the
intensity_level
field value of all target <Colour Index>
instances, thus controlling which
<Primitive Colour> instance is referenced
by each such <Colour Index> instance and/or
its intensity.
Note that since each controlled <Colour Index>
instance may be bound to a different
<Colour Table Group> instance, and thus
to a different primary <Colour Table> instance;
the fact that their index values are
the same does not mean that the set of
<Colour Index> instances controlled by a
given <Colour Index Control Link>
instance reference the same
<Primitive Colour> instance.
Primary Page in DRM Diagram:
Secondary Pages in DRM Diagram:
Example
Consider a <Geometry Model> component of a
<Model> instance representing a tree, in
which the geometry consists of a single
<Polygon> instance P defined with
an applicable <Stamp Behaviour> instance
as depicted in Figure 6.5:
Figure 5 — <DRM Colour Index Control Link> example
The appearance of P is determined by a
<Colour Index> component and
an <Image Mapping Function> component.
However, for every <Geometry Model Instance> instance
of this tree, the data provider wants to be able to vary the
intensity_level of
the <Colour Index> component, so that its contribution
to the overall colour of the tree changes from instance to instance.
Consequently, the <Colour Index> instance has a
<Colour Index Control Link> component, which specifies a
<Variable> component that controls the
intensity_level of the
<Colour Index> instance, so that each
<Geometry Model Instance> instance can supply its own
<Literal> component to determine the
proportional contribution of the <Colour Index> instance
to the appearance of P.
FAQs
-
What does a
<Colour Index Control Link>
instance control?
A <Colour Index Control Link>
instance controls, for each
target <Colour Index> instance,
the value of the index field,
the value of the
intensity_level field,
or both.
-
For a given target <Colour Index> instance X,
can a <Colour Index Control Link>
component be used to change which
<Colour Table> component is accessed within
the <Colour Table Group> instance
referenced by X?
No. The index field value of
X always refers to the
primary <Colour Table> component of the
<Colour Table Group> instance
associated to by X.
-
For a given target <Colour Index> instance X,
can a <Colour Index Control Link>
component be used to change which
<Colour Table Group> instance is
referenced by X?
No. The connection between X and the
<Colour Table Group> instance is
an association within the given transmittal, and associations cannot be
changed dynamically.
Constraints
Composed of (two-way) (inherited)
Component of (two-way)
Notes
Fields Notes
The description field
specifies a text description of the purpose of the
<Control Link> instance.
The colour_index
field specifies which <Expression>
component, if any, specifies the
index field value of the
affected <Colour Index> instances.
If this value is zero, the index
field values of the <Colour Index> instances
are not controlled.
The intensity_level_index
field specifies which
<Expression> component, if any, specifies the
intensity_level
field value of the affected
<Colour Index>
instances. If this value is zero, the
intensity_level
field values of the <Colour Index>
instances are not controlled.
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