[Radiance-general] Modeling glare from light fixtures

[Christopher Rush]

If you model estimated geometry surrounded by the "impostor surfaces," would this impact your results depending on how you are estimating glare? If you use luminance for glare evaluation, do you get the luminance value of the faux luminaire geometry behind the illum "impostor surface" or do you get the luminance value of the IES illum?

If you get the value of the IES file then the detailed geometry is just for show in any renderings. If you get the value of the detailed geometry then you're back to the question of if it's accurate.


-----Original Message-----
From: Randolph M. Fritz [mailto:RFritz at lbl.gov] 

For presentation, however, you may want to model the lamp and luminaire itself, as well as the IES file.  This will not be physically accurate, but is helpful in visualizing the glare.  To do this, you wrap the luminaire geometry in an illum (for fluorescents this is usually a long narrow box), to which you attach the IES data.  This is called an "impostor surface," because it is an impostor for the actual luminaire. 
 You then use glows within the illum to provide a visual representation of light within the luminaire.  Light from a glow does not pass through an illum and hence does not affect the lighting of the scene geometry or the glare calculation.
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