Class Name: Volume Light Behavior

Superclass - Light Rendering Behavior

Definition

A Volume Light Behavior is a light behavior whose color varies depending on your position relative to the light's location and to the volume's geometry. The volume surrounds the light. Within the volume, the light has the primary color; outside the volume it takes the secondary color.

Primary Page in DRM Diagram:

• 3

Example

1. The Volume Light Behavior has a primary color that is a Color Index that has an intensity attribute of 0.95. The Volume Light Behavior also has a secondary color. The minimum_color_intensity is 0.0. The use_full_intensity flag is false. The light is in the center of the volume and the volume is a Parallelepiped Volume Extent representing a cube measuring 2000m per side.

   if:
   eye_distance_from_light = the distance of the viewing position from the light
   volume_distance_from_light = the distance between the light and the volume boundary along the same vector
   then:
   final_intensity = minimum_color_intensity + (((volume_distance_from_light - eye_distance_from_light) / volume_distance_from_light) * (full_intensity - minimum_color_intensity))
   

   If my position from the light is a distance of 500m along a vector from the light to a corner of the volume then the final_intensity is 0.614.
   0.0 + (((1414.2 - 500.0) / 1414.2) * (0.95 - 0.0))
   

   If my position from the light is 3000m then the final_intensity is 1.0 (using the secondary color) because I am outside the volume and there is a secondary color on the Volume Light Behavior.

2. The Volume Light Behavior has a primary color that is an Inline Color (which makes the full intensity 1.0). The minimum_color_intensity is 0.5. The use_full_intensity flag is true. The light is in the center of the volume and the Volume Extent is a Spherical Volume Extent with a radius of 1000m.

   If my distance from the light is a distance of 100m then the final_intensity is 1.0, since my position is inside the volume and the use_full_intensity flag is set to true.

   If my distance from the light is a distance of 0 units then the final_intensity is 1.0 since my position is inside the volume and the use_full_intensity flag is set to true.

FAQs

Constraints

Composed of (one-way)

• one Location 3D (notes)
• one Volume Extent (notes)
• optionally, a World Transformation (notes)

Component of (one-way)(inherited)

• one or more Light Rendering Properties

Field Elements

Notes

Composed of Notes

Location_3D

 volume center

Volume_Extent

 volume shape

World_Transformation

 To locate and orient the volume within the currently scoped 'world'
 spatial reference frame

Fields Notes

use_full_intensity

 A flag, if true indicates that the full intensity of
 the light is shown within the volume. If this flag is
 false, then the intensity of the light decreases
 (towards the minimum_color_intensity value) as you
 move away from the light. The intensity of the light
 would reach the minimum_color_intensity value when
 you reach the boundary of the volume.

minimum_color_intensity

 This value (between 0.0 and 1.0) is used in conjunction
 with the intensity value of the primary color. If the
 primary color is a <Color Index> then the full intensity
 will be the intensity attribute of that class. If the
 primary color is an <Inline Color> then the full intensity
 is 1.0.
 If your location is the same as that of the light then you
 receive the full (intensity) value. As you move away from
 the light (but are still within the volume), the intensity
 decreases toward the minimum_color_intensity value (unless
 the use_full_intensity flag is TRUE). Once you get outside
 the volume, the intensity is that of the
 minimum_color_intensity value.
 If the minimum_color_intensity value is 0.0 and you're
 outside the volume, the secondary color will be seen. If
 no secondary color is used then nothing will be seen.