The SEDRIS Data Representation Model
APPENDIX A - Classes
Linear Geometry

Abstract Class Name: Linear Geometry

Superclass - <Primitive Geometry>

Subclasses

Definition

An instance of this DRM class is a geometric linear representation.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

  1. A <Line> instance can be rendered as a single light point, as depicted in Figure 6.28.

    Linear Geometry, Example 1

    Figure 28 — <DRM Linear Geometry> light point example

  2. A <Line> instance can be rendered as three line segments, as depicted in Figure 6.29.

    Linear Geometry, Example 2

    Figure 29 — <DRM Linear Geometry> line segment example

Constraints

Associated with (two-way)

Composed of (two-way) (inherited)

Composed of (two-way metadata) (inherited)

Component of (two-way) (inherited)

Inherited Field Elements

This class has no inherited field elements.

Field Elements

SE_Short_Integer_Unsigned count; 2
SE_Boolean suppress_last; 3

Notes

Composed of Notes


Union_Of_Primitive_Geometry

A <Primitive Geometry> instance P has a <Union Of Primitive Geometry> component only when P can be decomposed into nested <Primitive Geometry> instances.

EXAMPLE  A <Polygon> instance can be decomposed into multiple <Polygon> instances representing subfaces.

Fields Notes

count

The count field of a <Linear Geometry> instance indicates how the <Linear Geometry> instance is to be rendered. A count field value of zero for a given <Linear Geometry> instance L indicates that L is to be rendered as one solid line segment, and the suppress_last field does not apply.

If count is greater than zero and L has a <Light Rendering Properties> component, the following applies:

  1. count is the number of evenly spaced light points to be rendered along L.
  2. The distance between light points is calculated by dividing the total length of L by count - 1.
  3. If count is one, a single light point is placed at the halfway point of L and the suppress_last field does not apply.
  4. The fields of the <Light Rendering Properties> component are applicable to each light point as described in 4.15.3.6 Simulating lighting effects of ISO/IEC 18023-1.
  5. If a <Rendering Properties> component is present, it is applicable to each light point as described in 4.15.3.4 Lighting effects of ISO/IEC 18023-1.
  6. No additional factors apply.

If count is greater than zero and L does not have a <Light Rendering Properties> component, the following applies:

  1. count is the number of evenly spaced line segments to be rendered along L.
  2. The length of a segment is calculated by dividing the total length of L by count.
  3. If count is one, a single solid line segment is used and the suppress_last field does not apply.
  4. If a <Rendering Properties> component is present, it is applicable to each light point as described in 4.15.3.4 Lighting effects of ISO/IEC 18023-1.
  5. No additional factors apply.

suppress_last

If count is greater than one, the suppress_last field specifies whether the last segment or point in the sequence is suppressed or rendered.


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Last updated: July 26, 2006 Copyright © 2006 SEDRIS