Inputs
Drag the light source you want to evaluate from the Object Manager into this field to measure its lighting intensity.
With the help of this value, you can use the PLight node to control actions based on the brightness of a light source at a particular position in 3D space (defined by the Position values).
The node outputs a Boole value of either True or False depending on whether the light's intensity exceeds the Threshold value at this position in 3D space. The node's On port outputs the value False if the light's brightness is less than or the same as the Threshold, or True if it exceeds the Threshold. A Threshold of 1 equals a light intensity of 100%.
If you want to control actions based on the color of a light source at a particular position in 3D space (defined by the Position values), enable Color and set Threshold to 0 (if you don't set the Threshold to 0, the light's brightness will be evaluated also).
If you want to control actions based on a light's color and brightness, in addition set the Threshold value to the desired brightness. See Threshold, above. The node's On port will then only output the value True if the light's brightness exceeds the Threshold value and the light's color is the same/similar color as the Color setting.
The Color Variation setting defines how similar — defined as a percentage — the light's color and the Color setting must be in order to produce a True value. For example, with a value of 0%, the colors must match exactly in order to produce an output of True, while a value of 100% means the colors will match regardless.
This is the position at which the light intensity of the linked light source should be measures. Since the angle with which the incoming light falls also plays a role, an additional Normal vector setting is available that defines a surface Normal at the Position.
This vector setting defines the direction of a surface Normal that is calculated at the Position location. With this information, the angle of the incoming light can be included in the calculation of the brightness.
Enable this option, for example, if the light source also has animated parameters to ensure that the Node is updated automatically, even if nothing has changed with the Node's settings or the position or orientation of the light source.