The SEDRIS Data Representation Model
APPENDIX A - Classes
Colour Index Control Link
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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> within a
<Model> representing a tree, where the geometry
consists of a single Polygon defined with
<Stamp Behaviour>.
The Polygon's appearance is determined by a
<Colour Index> and an
<Image Mapping Function>. However,
for every
<Geometry Model Instance>
of this tree, the data provider wants to be able to vary
the intensity_level of
the <Colour Index>, so that
its contribution to the overall colour of the tree changes from
instance to instance. Consequently, the
<Colour Index> has a
<Colour Index Control Link>,
which specifies a <Variable> that controls
the intensity_level of
the <Colour Index>, so that each
<Geometry Model Instance>
can supply its own <Literal> to determine
the percent contribution of the
<Colour Index> to the appearance of the
Polygon.
FAQs
- What does a
<Colour Index Control Link> instance control?
A <Colour Index Control Link>
controls the value of the index
stored in a <Colour Index>, the value of
the intensity_level
stored in the <Colour Index>, or both.
- Can a
<Colour Index Control Link> instance be used to change which
<Colour Table> is accessed within a
<Colour Table Group>?
No. The index always
refers to the primary <Colour Table>.
- Can a
<Colour Index Control Link> instance be used to switch a
<Colour Index> from one
<Colour Table Group> to a different
<Colour Table Group>?
No. The link to the
<Colour Table Group> 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 given
<Control Link> instance's purpose.
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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Last updated: July 16, 2004
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Copyright © 2004 SEDRIS™
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