Select a parallel, point or spot light and click the Open Object 
edit button to open the Light Specification dialog.
You can also select 3D> Adjust Lights 
to access a list of the light sources present in the current plan and open the specification dialog for any of them. See "Adjust Lights Dialog".
In addition, you can right-click on a light in an unlocked library (see "Adding to the Library") or click on it and select Library> Edit Light Data to open a version of the Light Specification dialog that is similar to the Electrical Service Specification dialog. See "Light Data Tab".
Depending on the type of light selected, the options available may vary.
Type - Select a source type for the light. Available source types are Point Light, Spot Light, and Parallel Light. The selections in the dialog are affected by the Type that you select. Each type of light source behaves differently but they have some rendering properties in common. See "Defining Light Types".
Auto Intensity - Select the check box to have the program set intensities for each light in the render view. When you select Auto Intensity the program provides an average intensity to render with reasonable lighting effects. If you clear the check box, the slider bar controls how bright the light appears in the render view.
Lights that have an intensity of 0% are the same as lights that are turned off. Lights that have an intensity of 100% have the maximum brightness allowed. If you have multiple lights in a room all set to maximum intensity, it is possible to have too much light for a realistic View. Colors and textures become washed out if there is too much light.
Color - Click the rectangle to define the color of the light being modeled. Colored lights may be used to achieve special lighting effects. They alter the appearance of your material colors and textures.
The default color of light is pure white, which has the least affect on the material colors and textures.
Attenuated - Check this box to control how the quickly the light intensity drops off as a result of the distance from the light source. Only Spot and Point Lights can have attenuation values set.
The three edit values represent the three coefficients (a, b, and c) in the expression:
where d is the distance from the light source. Increasing any of these values results in the light intensity dropping off faster (the light does not travel as far). Decreasing any value results in the light intensity dropping off slower, (the light travels farther). Small changes in these coefficients can have significant impact on lighting effects. Some experimentation should be done to fully understand how to use them.
Floor Number - Define where the symbol for an added light displays in floor plan views.
The Floor Number controls which floor plan the added light symbol is drawn on. If you assign the number of a non-existent floor, you cannot see the light and you cannot delete that light.
A floor number of -1 draws the light symbol on all floors, a value of 1 draws the light symbol on the first floor. The floor number has no effect on the light height. Set the number equal to the floor plan that contains the room that the light is in, if you want it to display in floor plan view.
Height - Define a height for the light. Heights of Added lights are always relative to the first floor. If you want an Added light to display in a room on the second floor you must enter a height value that includes the first floor. A value of 0 equals the floor elevation of the first floor.
Tilt Angle - The Tilt Angle is used to control the angle of the light with respect to the horizon. A value of -90 degrees means that the light is pointing straight down and a value of 90 degrees means that the light is pointing straight up. 0 degrees is parallel to the horizon.
Dir Angle - Defines the angle that a Parallel or Spot Light is pointed along. Zero degrees is measured horizontally on your screen pointing to the right. Positive values rotate in a counter-clockwise direction from there. Enter a value up to 360 degrees. If you enter a negative value, the program uses Zero.
Direct a Spot Light in floor plan view by selecting and dragging the rotate handle.
Cut Off Angle - The Cut Off Angle controls the angle of the cone of light for Spot Lights only. A cone angle of 180 degrees would create a Spot Light that shines on one side of the light's position, representing a half sphere. A small cone angle, say 10 degrees, would create a very narrow cone of light. The cut off angle should always be between 0 and 180 degrees. The cut off angle for an added light can be defined in the floor plan view by dragging the handles at the ends of the cone lines in or out.
Drop Off Rate - This affects how fast the light intensity drops off from the center of the cone of light to the outside edge. This is only available for Spot Lights.
The default value for this is set to 7.5, which means the light drops off fairly quickly. It is not useful to set this value too low because there are limitations in the OpenGL lighting model that result in jagged looking circles of light when they are shining on large flat surfaces. Appearances can be improved by decreasing the Maximum Triangle Size and increasing the Drop off Rate but it is impossible to get a nice sharp circle of light using current methods under OpenGL.
Soft Shadows (raytracing) - This allows you to set how a light casts soft shadows in a Raytrace view. Setting the Light Size determines how big the light should appear. A size of zero indicates a true point light source, while a size of 3 indicates a larger source such as a lightbulb. Setting the Softness determines how many iterations the raytracer should go through to soften the light. This value determines the quality of the raytrace, but also slows down the raytrace. It is not recommended to use values greater than 2 or 3, unless the Light Size is very large.
On - This controls whether or not the light should be used for lighting effects in the render view. The default is "On".
Casts Shadows - Controls whether or not the light casts shadows when Shadows are turned on in a render view.
It is recommended that you only use one, or at most two lights to casts shadows at a time. Shadow calculations are very complicated and can slow rendering significantly.
Show Position in Render View - Check this box to display an indicator where a light source is actually positioned in a render view. The light position indicator is only drawn when the light is "On" and only for positional lights such as "point" or "spot" lights. This tool can be used to determine if your light source is positioned correctly.
Use in Real-Time Rendering/Use in Raytracing/Use in Both - These options allows you to specify whether a light is used only in a raytrace view, only in a render view, or used in both views. Raytrace views can handle many more lights than render views, and some fixtures may have four or five lights in a raytrace view while only one in a render view. Be warned that the more lights you use in either view, the slower the time to generate that view.
For information about the Layer tab, see "Layer Tab".
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