The SEDRIS Data Representation Model
APPENDIX A - Classes
Colour Index Control Link

Class Name: Colour Index Control Link

Superclass - <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

  1. 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 5:

    Colour Index Control Link, Example 1

    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)

Inherited Field Elements

SE_String

description;

1

Field Elements

SE_Integer_Unsigned

colour_index;

2

SE_Integer_Unsigned

intensity_level_index;

3


Notes

Fields Notes

description

The description field specifies a text description of the purpose of the <Control Link> instance.

colour_index

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.

intensity_level_index

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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