2013

Photometry
Photometry is available when the LIGHTINGUNITS system variable is set to
1 or 2. Photometry is the measurement of the luminous intensities of visible
light sources.
In photometry, luminous intensity is a measure of the perceived power emitted
by a light source in a particular direction. Luminous flux is the perceived
power per unit of solid angle. The total luminous flux for a lamp is the
perceived power emitted in all directions. Luminance is the total luminous
flux incident on a surface, per unit area.
Intensity Enter an intensity value in candelas, the perceived power in a
luminous flux value, or illuminance value for the total luminous flux incident
on a surface.
 Candela (symbol: cd) is the SI unit of luminous intensity (perceived power
emitted by a light source in a particular direction). Cd/Sr
 Lux (symbol: lx) is the SI unit of illuminance. Lm/m^2
 Foot-candle (symbol: fc) is the American unit of illuminance. Lm/ft^2
Enter f to specify the perceived power in a luminous flux value.
If you enter i, you can specify the intensity of the light based on an
illuminance value.
The illuminance value can be specified in either lux or foot-candles. Enter d
to specify a distance to use to calculate illuminance.
Color Specify the color of the light based on a color name or a Kelvin
temperature.
Enter ? to display a list of color names. Enter a text string using wild card
characters to display a partial listing of color names, or an asterisk (*) to display
all the possible choices.
If you enter k, you can specify the color of the light based on a Kelvin
temperature value.
Exit Exits the command.
Shadow
Makes the light cast shadows.
Off Turns off the display and calculation of shadows for the light. Turning
shadows off increases performance.
Sharp Displays shadows with sharp edges. Use this option to increase
performance.
Soft Mapped Displays realistic shadows with soft edges.
1076 | Chapter 2 Commands