The SEDRIS Data Representation Model
APPENDIX A - Classes
Distance LOD Data

Class Name: Distance LOD Data

Superclass - <Base LOD Data>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class specifies a level of detail described in terms of distance from the eyepoint to the centre of the object.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

This class appears on only one page of the DRM class diagram.

Example

  1. Consider a <LOD Related Geometry> instance which has two branches, each having an attached <Distance LOD Data>.

    The first <Distance LOD Data> instance has:
    minimum_range = 100.0
    minimum_fade_band = 10.0
    maximum_range = 200.0
    maximum_fade_band = 20.0

    The second <Distance LOD Data> instance has:
    minimum_range = 200.0
    minimum_fade_band = 10.0
    maximum_range = 1000.0
    maximum_fade_band = 10.0

    If the eyepoint is moving outward and the distance reaches 90, the first branch starts fading in. At a distance of 100, the first branch has totally faded in. At a distance of 180 the first branch starts to fade out. At a distance of 190 the second branch starts fading in. The first and second branches are both seen (super-imposed) between the ranges of 190 and 200. At a distance of 200 the first branch is totally faded out, while the second branch is the only branch seen. At a distance of 990, the second branch starts fading out, and at 1000 it is completely faded out.

  2. Consider a <Level of Detail Related Geometry> instance which has two branches, each having an attached <Distance LOD Data>.

    The first <Distance LOD Data> instance has:
    minimum_range = 50.0
    minimum_fade_band = 20.0
    maximum_range = 100.0
    maximum_fade_band = 30.0

    The second <Distance LOD Data> instance has:
    minimum_range = 110.0
    minimum_fade_band = 15.0
    maximum_range = 500.0
    maximum_fade_band = 10.0

    If the eyepoint is moving outward and the distance reaches 30, the first branch starts fading in. At a distance of 50, the first branch has totally faded in. At a distance of 70 the first branch starts to fade out. At a distance of 95 the second branch starts fading in. The first and second branches are both seen (super-imposed) between the ranges of 95 and 100. At a distance of 100, the first branch is totally faded out, while the second branch is the only branch seen, but hasn't completely faded in. At a distance of 110 the second branch has completely faded in. At a distance of 490 the second branch starts fading out, and at 500 is completely faded out.

  3. A set of polygonal data is produced with low detail for viewing at ranges greater than 3200 metres, and organized as a <Union Of Primitive Geometry>, with a <Distance LOD Data> component specifying this viewing range so that the intended viewing distance at which these <Polygon> instances are to be used is provided.

  4. See <LOD Related Geometry>'s examples.

FAQs

As a data provider, I have a branch of a distance level-of-detail-related organization for which fade bands aren't applicable. How should those fields be set?

If a target does not contain fade bands, then the minimum_fade_band and maximum_fade_band shall be set to zero (0).

Constraints

Composed of (two-way)

Component of (two-way) (inherited)

Inherited Field Elements

This class has no inherited field elements.

Field Elements

SE_Long_Float minimum_range; (notes)
SE_Long_Float minimum_fade_band; (notes)
SE_Long_Float maximum_range; (notes)
SE_Long_Float maximum_fade_band; (notes)

Notes

Composed of Notes


Location

 If present, the <Location> component is the centre point for
 the LOD test.

Fields Notes


minimum_range

 The minimum_range field is specified in metres.

minimum_fade_band

 The minimum_fade_band is expressed in metres (not percent).
 This fade band shall go in the negative direction from the
 minimum range.

maximum_range

 The maximum_range field is specified in metres;
 SE_POSITIVE_INFINITY is a legal range value.

maximum_fade_band

 The maximum_fade_band is expressed in metres (not percent).
 This fade band shall go in the negative direction from the
 maximum range.
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Last updated: July 16, 2004 Copyright © 2004 SEDRIS™