2012

Set the Type of Lighting
AutoCAD offers three choices for lighting units: standard (generic),
International (SI), and American. The standard (generic) lighting workflow is
equivalent to the lighting workflow in AutoCAD prior to AutoCAD 2008. The
default lighting workflow for drawings created in AutoCAD 2008 and later is
a photometric workflow based on International (SI) lighting units. This choice
results in physically correct lighting. The American lighting unit provides
another option. American differs from International in that illuminance values
are formatted in foot-candles rather than lux.
In previous versions of AutoCAD, standard lighting was the default. You can
change the type of lighting with the LIGHTINGUNITS system variable. The
LIGHTINGUNITS system variable set to 0 represents standard (generic) lighting;
set to 1 represents photometric lighting in American units; set to 2 represents
photometric lighting in International SI units.
Photometric Lights
Photometric lights are physically correct lights. Physically correct lights
attenuate as the square of the distance.
Photometric properties can be added to both artificial lights and natural lights.
Natural lights are the sun and the sky. The natural lighting is represented
interactively by a viewport background type.
You can create lights with various distribution and color characteristics, or
import specific photometric files available from lighting manufacturers.
Photometric lights always attenuate using an inverse-square falloff, and rely
on your scene to use realistic units.
Tone Mapping
Generally with photometric lights and especially the sun you need to perform
tone mapping. Tone mapping can be adjusted with the RENDEREXPOSURE
command. The Adjust Rendered Exposure dialog box provides a preview and
controls to adjust the tone mapping.
To set the drawing for standard lighting workflow
Do one of the following:
■ Click Render tab ➤ Lights panel ➤ Lighting Units drop-down ➤ Generic
Lighing Units.
No lighting units are used and standard (generic) lighting is enabled.
2148 | Chapter 44 Add Lighting to Your Model