Control Light Properties

Control Light Properties

Each light you add to the drawing is listed by name and type in the Lights in Model palette ( LIGHTLIST). Lights in blocks and xrefs, the sun, and default lighting are not included.

When a light is selected in the list, it is selected in the drawing and vice versa. The properties of the lights in the list are saved per drawing. All properties can be changed in the Properties palette. When a light is selected in the drawing, you can use grip tools to move or rotate the light and change some other properties, for example, the hotspot and falloff cone in spotlights. You can see the effect on the model as you change the properties of a light.

General Properties

The following properties are common to all lights and are located in the General panel of the Lighting Properties palette. Full descriptions of the controls are located under the Properties command in Lighting Properties:

• Name. Specifies the name assigned to the light.
• Type. Specifies the type of light: point light, spotlight, distant light, or web.
• On/Off Status. Controls whether the light is turned on or off.
• Shadows. Controls whether the light casts shadows. To be displayed, shadows must be turned on in the visual style applied to the current viewport. Turn shadows off to increase performance.
• Intensity factor. Sets a multiplier that controls brightness. Intensity is not related to attenuation.
• Filter color. Sets the color of the light emitted.
• Plot glyph. Allows the ability to plot the drawing with the light glyphs on.

Spotlight Hotspot and Falloff Under General Properties

When light from a spotlight falls on a surface, the area of maximum illumination is surrounded by an area of lesser intensity.

• Hotspot cone angle. Defines the brightest part of a light beam. Also known as the beam angle.
• Falloff cone angle. Defines the full cone of light. Also known as the field angle.
• Rapid decay area. Consists of the region between the hotspot and falloff angles.

The greater the difference between the hotspot and falloff angles, the softer the edge of the light beam. If the hotspot and falloff angles are near equal, the edge of the light beam is sharp. Both values can range from 0 to 160 degrees. You can adjust these values directly with the Hotspot and Falloff grips.

Photometric Properties

Photometric lighting offers additional properties that make the lighting different than standard lighting. The following properties are under the Photometric properties panel:

• 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.)

If you select Web in the Type property for a photometric light, additional properties are offered in the Photometric Web and Web offsets panel in the Lighting Properties palette.

• Web file. Specifies the data file describing the intensity distribution of the light.
• Web preview. Displays a 2D slice through goniometric data.
• Rotation of X. Specifies a rotational offset of the web about the optical X axis.
• Rotation of Y. Specifies a rotational offset of the web about the optical Y axis.
• Rotation of Z. Specifies a rotational offset of the web about the optical Z axis.

Geometry Including Target Properties

The Geometry panel provides controls for the location of the light. If the light is a target point light, spotlight, or weblight additional target point properties are available. A light can be changed to a light with target properties or changed from a light with target properties to one without by selecting either Yes or No in the Targeted property.

Attenuation (Point Lights and Spotlights)

Attenuation controls how light diminishes over distance. The farther away an object is from a light, the darker the object appears. You can specify no attenuation, inverse linear, or inverse squared ( POINTLIGHT, SPOTLIGHT). Attenuation is not active for photometric lights.
Another way to control the start point and end point of light is to use limits. Limits work like clipping planes to control where light is first emitted and where it stops. Using limits can increase performance by removing the need for the program to calculate light levels where the light is already practically invisible.