Table 6.260 — DRM_Spot_Light
Property |
Description |
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Class |
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Superclass |
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Subclass |
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Definition |
An instance of this DRM class is a <DRM Base Positional Light> instance that specifies an elliptical cone of influence, the tip of which is the specified <DRM Location 3D> component. The elliptical cone is bounded where it intersects the sphere centred at the tip with radius as specified by the radius field. This results in a truncated elliptical cone. Only objects located within this elliptical cone are affected by the light. The location of the spot light is specified by the <DRM Location 3D> component. The shape and orientation of the spot light is specified by the <DRM Lobe Data> component L as follows:
These provide the necessary information to position the spot light in the currently applicable SRF, orient the spot light with respect to its VERTICAL_AXIS vector, and identify the direction in which the spot light is pointing. The lobe shape is centred horizontally and vertically around the LIGHT_DIRECTION vector, with origin at the location specified by the <DRM Location 3D> component. The intensity dropoff is computed as follows. Given a point on a ray in the cone at fixed distance D from the cone apex, if
then the intensity I at the point is:
The horizontal_drop_off_rate field specifies, in radians, the horizontal angular intensity distribution of the light. The higher this value, the more focused the light. A value of 0,0 specifies a light that equally illuminates all objects within the cone of influence, and instantly falls to an intensity of 0,0 at the edge of the cone of light. The vertical_drop_off_rate specifies, in radians, the vertical angular intensity distribution of the light. The higher this value, the more focused the light. A value of 0,0 specifies a light that equally illuminates all objects within the cone of influence, and instantly falls to an intensity of 0,0 at the edge of the cone of light. |
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Class diagram |
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Inherited field elements |
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Field elements |
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Default field values |
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Associated to (one-way) (inherited) |
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Associated to (one-way) |
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Associated by (one-way) (inherited) |
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Associated by (one-way) |
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Associated with (two-way) (inherited) |
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Associated with (two-way) |
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Composed of (two-way) (inherited) |
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Composed of (two-way) |
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Composed of (two-way metadata) (inherited) |
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Composed of (two-way metadata) |
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Component of (two-way) (inherited) |
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Component of (two-way) |
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Constraints |
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Clarifications |
1A <DRM Classification Data> component, if present, allows a data provider to specify whether the <DRM Light Source> instance represents an environmental object, such as the sun. 2If a <DRM Light Source> instance is to be turned on and off dynamically, it has a <DRM Light Source Control Link> component to express that control mechanism. 3The <DRM Location 3D> component specifies the position of the <DRM Base Positional Light> instance. 4The <DRM Lobe Data> component specifies the lobe shape. |
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Example(s) |
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