Point Lights
A normal point light does not target an object, but illuminates everything around it. Use such point lights for general lighting effects.
A target point light has additional target properties so it can be directed to an object. It can also be created from a point light by changing the target property of the point light from No to Yes.
In the standard lighting workflow, you can set a point light manually so its intensity diminishes with respect to distance either linearly, according to the inverse square of the distance, or not at all. By default, the attenuation is set to None.
Point Lights in Photometric Workflow
A free point light can have photometric distribution properties. The attenuation for a photometric point light is always set to inverse square.
When the LIGHTINGUNITS system variable is set to 1 (American units) or 2 (International SI units) for photometric lighting, additional properties are available for a point light. The following photometric properties can be set via the Properties Inspector palette:
- Lamp Intensity. Specifies the inherent brightness of the light. Specifies the intensity, flux or illuminance of the lamp.
- Resulting Intensity. Gives the final brightness of the light. (Product of lamp intensity and intensity factor. Read-only.)
- Lamp Color. Specifies the inherent color of the light in Kelvin temperature or standard.
- Resulting Color. Gives the final color of the light. This is determined by a combination of the lamp color and the filter color. (Product of lamp color and filter color. Read-only.)
When the drawing lighting units are photometric, the attenuation type property becomes disabled. Photometric lights have fixed, inverse-square attenuation.
The following image is an example of a photometric point light and lighting properties palette with the photometric properties outlined:
