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The SEDRIS Data Representation Model
APPENDIX A - Classes Light Rendering Properties Control Link |
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An instance of this DRM class is a specialized <Control Link> instance providing the connection between one or more <Light Rendering Properties> instances and the <Expression> instances that are used to determine whether the target <Light Rendering Properties> instances are active and/or their candela_value field values are varying.
Consider a flight simulator database containing an area of terrain representing a city as seen from the air. Some of the <Polygon> instances of this terrain representation have <Light Rendering Properties> instances with <Twinkling Light Behaviour> components, representing city lights. These <Light Rendering Properties> instances share a <Light Rendering Properties Control Link> component that turns them on and off depending on the time of day (on at dusk, off at dawn).
Consider a runway, bordered on each side by a <Line> instance representing the runway lights. Each <Line> instance has a <Light Rendering Properties> component with a <Strobing Light Behaviour> component, and a <Light Rendering Properties Control Link> component that turns the lights on and off depending on the time of day (on at dusk, off at dawn).
A <Light Rendering Properties Control Link> instance controls whether the associated <Light Rendering Properties> instances are on or off, and the candela_value of the <Light Rendering Properties> instances.
No. The links to the <Light Rendering Behaviour> instances are associations within the transmittal, and associations cannot be changed dynamically.
The description field specifies a text description of the purpose of the <Control Link> instance.
The active_expression_index field specifies which <Expression> component, if any, specifies the active_light_value of the target <Light Rendering Properties> instances. If active_expression_index is zero (0), the active_light_value field values of the target instances are not controlled. Otherwise, the value is a one-based index into the ordered aggregation of <Expression> instances.
The candela_value_expression_index field specifies which <Expression> component, if any, specifies the candela_value of the target <Light Rendering Properties> instances. If candela_value_expression_index is zero (0), the candela_value field values of the target instances are not controlled. Otherwise, the value is a one-based index into the ordered aggregation of <Expression> instances.
The lower_candela_value_index field specifies which <Expression> component, if any, specifies the lower limit of the candela_value of the target <Light Rendering Properties> instances. If lower_candela_value_index is zero (0), no lower limit is specified. Otherwise, the value is a one-based index into the ordered aggregation of <Expression> instances.
NOTE 1 If candela_value_expression_index is zero, the candela_value field values of the target instances are not controlled, so the lower_candela_value_index value is also zero.
The upper_candela_value_index field specifies which <Expression> component, if any, specifies the upper limit of the candela_value of the target <Light Rendering Properties> instances. If upper_candela_value_index is zero (0), no upper limit is specified. Otherwise, the value is a one-based index into the ordered aggregation of <Expression> instances.
NOTE 2 If candela_value_expression_index is zero, the candela_value field values of the target instances are not controlled, so the upper_candela_value_index value is also zero.
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