[Radiance-general] Error: Rendering with Radiance p. 319 Luminaire Modeling

[Greg Ward]

Hi Randoph,

Could you be more specific?  The radius of a sphere whose *projected* area is 1.0 for any distant point is sqrt(1/pi) as Chas derived it.  This is in fact what ies2rad needs.  This is not the same as a sphere whose total surface area is 1.0, which is the value you derived.

Is there an error in ies2rad.c, somewhere?

-Greg

> From: "Randolph M. Fritz" <RFritz at lbl.gov>
> Date: February 6, 2012 3:59:10 PM PST
> 
> I just had occasion to go through Chas. Ehrlich's luminaire modeling procedure given in *Rendering with Radiance* and there is an error on page 319 of the text. The radius of a unit sphere is 0.282095, not 0.56419. Both the number in the text and the ies2rad command are wrong.
> 
> Ouch!
> -- 
> Randolph M. Fritz