Summary

Dialog box for setting the Lamp Intensity for a photometric light.

List of Options

The following options are displayed.

Lamp Intensity

Represents the brightness of a lamp. More specifically, it represents the luminous intensity, or power in a particular direction. It is specified in candela by default (in both the SI and American units systems). Must select from one of the following radial buttons:

• Intensity (Candela). Specifies the number of candelas (cd) is the SI unit of luminous intensity (perceived power emitted by a light source in a particular direction).
• Flux (Lumen). Represents the rate of total energy leaving the lamp. It is specified in lumens (SI and American). Mathematically, the flux is the integral of the luminous intensity over the sphere. The calculation of flux depends on the distribution of intensities. For a point light with constant intensity, the flux is simply the product of the intensity and the solid angle of a sphere: 4 Pi * Intensity. For a spot light, the flux is the product of the intensity and the solid angle of the hotspot cone, plus the incremental solid angle of the fall-off region. For a weblight, there isn’t any analytical formula. The flux is obtained by numerically integrating the intensities provided in the web file.
• Illuminance (Foot-candles). Represents the energy per area arriving at a surface (Area-flux-density). It is specified in lux (SI) and foot-candles (American). For a near light, because the light rays are diverging, you have to talk about the illuminance at a specific distance from the lamp. So this requires an extra control to specify this distance and an additional affordance in the viewport to show the distance.

Intensity Input Control

Controls the intensity value.

Distance

When Illuminance is selected, displays the lux as a distance glyph in the viewport for the given light. Note: the text for the illuminance radio button will depend on the current lighting units. For the SI system, this will be “Illuminance (Lux),” and for the American system, it will be “Illuminance (Footcandles).” The distance field represents a world distance and should be formatted in the current length unit corresponding to the current lighting units. The distance field represents a world distance and should be formatted in the current length unit corresponding to the current insertion units controlled by the INSUNITS systems variable.

Resulting Intensity

Specifies the type of light. Determines the distribution of light from the lamp. The type of lighting can be changed after the light has been added to the drawings.

• Intensity Factor. Specifies the intensity factor.
• Resulting Intensity.Displays the resulting intensity of a light as the product of the Lamp Intensity value and the Intensity Factor. The value is read-only.