Table 6.24 — DRM_Blend_Directional_Light

Property

Description

Class
  • <DRM Blend Directional Light>

Superclass

Subclass
  • None.

Definition

An instance of this DRM class is a <DRM Directional Light Behaviour>, the intensity of which varies depending on the observer's position relative to the light's location, direction, and shape. This light takes the shape of a pyramid, subdivided by two planes. These planes are based at the pyramid's apex and extend towards the base. They subdivide the pyramid into upper and lower sections with a blend section in between. The upper section receives the primary colour, while the lower section receives the secondary colour. The blend section blends between the primary and secondary colours depending on the viewing position.

Class diagram

Figure 6.22 — DRM_Blend_Directional_Light

Inherited field elements

Field name

Range

Field data type

None

    

Field elements

Field name

Range

Field data type

upper_plane_angular_offset1

 

Long_Float

lower_plane_angular_offset2

 

Long_Float

Associated to (one-way) (inherited)
  • None.

Associated to (one-way)
  • None.

Associated by (one-way) (inherited)
  • None.

Associated by (one-way)
  • None.

Associated with (two-way) (inherited)
  • None.

Associated with (two-way)
  • None.

Composed of (two-way) (inherited)

Composed of (two-way metadata) (inherited)
  • None.

Composed of (two-way metadata)
  • None.

Component of (two-way) (inherited)

Component of (two-way)
  • None.

Constraints

Clarifications

1 This specifies the angular offset of the plane separating the upper and blend sections, in degrees (-180 to 180) from the given <DRM Lobe Data> instance's LIGHT_DIRECTION vector, measured along its VERTICAL_AXIS vector.

The resulting upper section of the light is taken to be between the plane and the positive end of the vertical axis vector.

2 This specifies the angular offset of the plane separating the lower and blend sections, in degrees (-180 to 180) from the given <DRM Lobe Data> instance's LIGHT_DIRECTION vector, measured along its VERTICAL_AXIS vector.

The resulting lower section of the light is taken to be between the plane and the negative end of the vertical axis vector.

3 This specifies the lobe shape.

Example(s)

  • Consider a <DRM Blend Directional Light> instance with both a primary and a secondary colour.

    Blend Directional Light, Example 1

    Figure 6.23 — <DRM Blend Directional Light> example

    At 10 degrees from the LIGHT_DIRECTION vector in the vertical direction, towards the positive end of the vertical axis vector, the primary colour is visible, because the position lies in the upper section of the pyramid, inside the lobe.

    At 10 degrees from the LIGHT_DIRECTION vector in the vertical direction, towards the positive end of the vertical axis vector, the primary colour is visible, because the position lies at the upper edge of the blend section. Moving from this position along the vertical axis vector toward the negative end, the amount of primary colour decreases as it is blended with proportionally increasing amounts of the secondary colour, because this lies within the blend section of the pyramid, from the upper edge to the lower edge. At -0,5 degrees from the LIGHT_DIRECTION vector in the vertical direction (that is, towards the negative direction of the vertical axis), the primary and secondary colours are blended in equal amounts, since this position is in the middle of the blend section. Moving in the same direction, the amount of primary colour continues to decrease proportionally as the amount of secondary colour increases. At -2,5 degrees from the light direction, only the secondary colour is visible, as this is the lower edge of the blend section.

    At -10 degrees from the LIGHT_DIRECTION vector in the vertical direction, that is, towards the negative end of the vertical axis vector, the secondary colour is visible, as this lies in the lower section of the pyramid.

    At -50 degrees from the LIGHT_DIRECTION vector in the vertical direction, that is, towards the negative end of the vertical axis vector, nothing is visible, since this lies outside the pyramid.