Today's good question comes from Ivana, who asked why she could no longer edit the Sun Properties Color in AutoCAD 2008. The color is displayed in the Properties window but it is greyed out.
A new variable, LIGHTINGUNITS, was added in AutoCAD 2008 to support photometric lighting. When that variable is enabled, the Sun color can not be edited. If you change the value of LIGHTINGUNITS to 0, photometric lighting is disabled and you can specify the Sun color as you did in the past.
Here is more information from the AutoCAD 2008 Help system:
LIGHTINGUNITS
Controls whether generic or photometric lights are used, and indicates the current lighting units
When this system variable is set to 1 or 2, photometric lighting is enabled; otherwise standard (generic) lighting is used.0 No lighting units are used and standard (generic) lighting is enabled
1 International lighting units are used and photometric lighting is enabled
2 American lighting units are used and photometric lighting is enabled
Thanks to Ivana for the good question and Lance (from the AutoCAD team) for helping find the answer.
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