Abstract Class Name: Directional Light Behaviour

Superclass - <Light Rendering Behaviour>

Subclasses

• <Blend Directional Light>
• <Cone Directional Light>
• <Pyramid Directional Light>

Definition

Directional lights have a direction and lobe shape defined by a component <Lobe Data> instance. The lobe shape parameters are used by sub-classes to specify cones, pyramids, blend geometry, etc.

Directional lights can have both a primary and a secondary colour. These are specified by the <Colour> components of the parent <Geometry> that have colour_mapping values of SE_CLR_MAPNG_LGT_RENDER_BHVR_PRIMARY and SE_CLR_MAPNG_LGT_RENDER_BHVR_SECONDARY, respectively.

Primary Page in DRM Diagram:

• 3

Secondary Pages in DRM Diagram:

Example

See concrete subclasses for examples.

FAQs

How can a simple bi-directional light be represented?

This can be done using either a <Cone Directional Light> or a <Pyramid Directional Light> with primary and secondary colours. Set the horizontal and vertical widths of the lobe to 180 degrees and invisible_behind to SE_TRUE.

Why does <Directional Light Behaviour> have a required <Location> component? Is it the location of the light?

No; it does not represent the location of any light(s) that use this behaviour. It is the reference location for the direction of the light (as expressed the <Reference Vector> components of the <Lobe Data>).

In most Spatial Reference Frames (SRFs), directions shall refer to a location to account for the curvature of the earth. Even in linear space SRFs, localized directions may be important (See Example 1).

Constraints

Composed of (two-way)

• one <Lobe Data> instance (notes)
• one <Location> instance

Component of (two-way)(inherited)

• one or more <Light Rendering Properties> instances

Inherited Field Elements

Notes

Composed of Notes

Lobe_Data

 This specifies the lobe shape.