Inserting a Custom Light

A custom light source’s emission distribution can be defined by a standard intensity distribution profile for accurate physical lighting.

To create a custom light:

1. Select the Light tool from the Visualization tool set, and then select Custom Light from the Tool bar.

2. Specify the custom light parameters by selecting Preferences from the Tool bar.

The Custom Light Data dialog box opens. Click Load Distribution and specify the location of the custom light distribution file, and then specify any additional custom light parameters.

Click to show/hide the parameters.

Parameter	Description
Light Rotation Angle	Specifies the rotation angle of the light source around an axis connecting the light location to the light target; this angle defines the reference plane for the intensity distribution curve
Distribution File	Displays the distribution file name when a valid distribution file has been selected, or “None” if a valid distribution file has not been designated (click Load Distribution to specify a file)
Load Distribution	Loads light emission profile data from a standard file. The brightness value is obtained using the integral of the raw emission data provided with the file. The file must be a text file with industry standard intensity distribution data in .ies format.
Distance Falloff	Select the distance falloff function (rate of intensity change while moving along the beam away from the light source)
Direction	Specifies the light’s direction by either specifying the light angle or vector
Angle	Sets the light’s angle by pan and tilt. The pan angle is based on an angle of 0 degrees at the positive Y axis, and is positive in a counter-clockwise direction; the tilt angle is equal to 0 at the horizontal plane, positive when pointing below the plane, and negative when pointing above the plane.
Vector	Indicates the direction of the light by specifying the coordinates of its X, Y, and Z vectors

3. Click OK.

The Light Preferences - Custom Light dialog box opens. Specify additional custom light parameters. Emitter parameters are specified by the distribution file, and cannot be changed.

Click to show/hide the parameters.

Parameter	Description
On/Off	Shows or hides the light produced by the light source
Color	Specifies a color associated with the light source; click the color box to select the color. This parameter is not available if a Color Temperature is specified.
Cast Shadows	Creates shadows
Dimmer	Dims the light source brightness (intensity); enter a percentage or drag the slider bar. Only the brightness of the light source is affected; the color temperature is not changed.
Use Emitter	A custom light’s actual brightness and color temperature must be specified, so this setting is not optional
Get Brightness From	Specifies the luminous quantity of the area or line light as a manually entered value or from a loaded distribution file
User Input	Manually specifies the brightness in Lux or Lumens
Distribution File	Sets intensity distribution data with a standard file specified in Custom Light Specs. The brightness value is obtained using the integral of the raw emission data provided with the file.
Color Temperature	Specifies the light color temperature in Kelvin. This refers to an ideal black body emitter, glowing “red hot” or “white hot.” A lower temperature generates an orange color; the hotter the temperature, the closer to white the color of the light is (see Correlated Color Temperature for typical light source color temperature ranges). Specifying this parameter is optional. If not specified, the default temperature is 0, meaning that the final emission color for the light is entirely controlled by the selection in Color. When the temperature is specified, Color cannot be changed. The final emission color is set by the Color Temperature. Color temperature settings can be white-balanced on a per-layer basis; see Setting Lighting Options.
Custom Light Specs	Specifies additional custom light options and loads a distribution file

4. Click OK to return to the drawing.

5. Click in the drawing to insert the custom light.

The custom light object is represented by a pair of perpendicular arrow-head vectors and two perpendicular circles. The black vector points to the target location; its axis line (the light axis) connects the light source location to the target. The red vector starts at the light source location, pointing to a reference point on the “equator” of the polar intensity distribution. Also known as the “zero angle line,” it represents the origin for measuring the intensity on the light curve.

The two vectors form the black circle, and the red circle is perpendicular to it. The black circle represents the original plane where the light curves are located. The red circle constrains the movement of the zero angle line.

After a custom light has been placed, the light parameters can be edited in the Object Info palette.

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Light Source Properties

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