[Radiance-general] accounting for irradiance due to ultraviolet in rtrace

[Greg Ward]

Hi Robert,

Radiance doesn't explicitly define wavelength ranges or anything of the sort.  By convention, the three channels provided are typically used for RGB data in a color space that is close to (but unfortunately not exactly equal to) the CCIR-709 primaries used by sRGB.  This is the assumption if no other information is given in a Radiance RGBE image. 

However, you can redefine these channels to mean whatever you like.  Since Radiance treats them independently in its calculations, as it has no wavelength-dependent simulations, it really doesn't matter.  You will of course need to define your materials differently with appropriate reflectances and transmittances for UV instead of visible, but the rest should just work.

The important caveats to remember are that for IR radiation, surface temperature matters, and Radiance does not computer or keep track of that.  In the case of UV, Radiance does not simulate phosphorescence, which may or may not matter to you.

Best,
-Greg

> From: Robert Ong <robert.harsono.ong at gmail.com>
> Date: October 23, 2011 6:56:01 PM PDT
> 
> Hi Lars,
> 
> Thanks for the feedback.
> 
> Do you mind if I ask how to define the wavelength range in Radiance? UV spectrum is normally starts from 120 to 400nm.
> 
> Thanks once again.
> 
> Kind Regards,
> Robert