Autodesk LIGHTSCAPE, Manual

Page: 145 / 362

Setting Photometric Properties
137
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Luminous flux is measured in lumens (lm).
Illuminance at a Distance
Illuminance at a distance is the illuminance caused by
the light shining on a surface at a certain distance and
facing in the direction of the source.
This intensity setting is measured in either footcan-
dles (fc) or lux (lx), depending on whether you are
working in American or International lighting units.
The distance is measured in the current units of the
model.
Note: The unit settings can be adjusted in the Docu-
ment Properties dialog by choosing Edit | Properties
and then clicking the Units tab.
Adjust Intensity
Adjust intensity allows you to scale the current lumi-
nous intensity, based on the maximum luminous
intensity. In the Solution stage, this slider can act as a
“dimming” control for a luminaire.
To set the intensity magnitude for a luminaire
definition:
1.
In the Luminaire Properties dialog, select an item
from the Magnitude list.
2.
Enter an intensity value (and a distance if you
have selected Illuminance at a Distance as the Magni-
tude setting).
3.
Click Apply to update the luminaire intensity.
Defining Intensity Distribution
Intensity distribution defines how the light is
dispersed from the luminaire. The available intensity
distribution types depend on the selected source
type.
Note: You can define intensity distributions in both
the Preparation stage and the Solution stage.
The intensity distribution types are:
• Isotropic
• Diffuse
• Spot
• Photometric Web.
Isotropic
Select this type to distribute the light equally in all
directions. Isotropic distribution is valid only for
Point source types.
To define an isotropic distribution:
1. In the Luminaire Properties dialog, select Point
from the Source Type list.
2.
Select Isotropic from the Distribution list.
3.
If necessary, adjust the Intensity Magnitude.
4.
Click Apply to update the luminaire definition.
Diffuse
Select this distribution type to emit light from a
surface with the greatest intensity at right angles to
that surface. The intensity falls off at increasingly
Magnitude
list
Orthographic view of a
Point source type set to
Isotropic distribution.