[Radiance-general] Re: direct/indirect photometric

[Greg Ward]

Hi John,

You have a point, especially since the illum sphere will never be 
subdivided during source sampling -- i.e., its distribution will always 
eminate from a point.  However, you must do one thing if you substitute 
the geometry for a fixture; you must multiply the A1 scalefactor in the 
brightdata primitive by the ratio of the illum sphere area divided by 
the illum replacement geometry area, or the total lumens will not be 
maintained during the switch.  Alternatively, you can specify an illum 
radius whose area (4*PI*radius^2) exactly equals the area of the 
replacement geometry.

-Greg

> From: John An <whollycow@mac.com>
>
> Wouldn't I need to modify the illum sphere when I'm creating a linear 
> fluorescent luminaire so that the illum geometry fits tightly around 
> the long luminaire?  Is it ok to create a sphere with a radius of 2 
> feet for a 4 feet long luminaire, and then just leave it alone?