[Radiance-general] rtrace -i -I flags

Giulio Antonutto Giulio.Antonutto at arup.com
Fri Mar 2 15:43:26 CET 2007

option -I

you want illuminance at 0 0 0 looking up (0 0 1), you sensor is at 0 0 0
and has the photocell up.




option -i

you want to measure that object you can see in direction (1 1 1) from
point 0 0 0. The meter is on the object you are looking at.

(similarly to when you run rpict -i, you get the illuminance over what
you see)


hope this makes is clearer...







From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org] On Behalf Of Jelle
Feringa / EZCT Architecture & Design Research
Sent: 02 March 2007 14:38
To: radiance-general at radiance-online.org
Subject: [Radiance-general] rtrace -i -I flags




I'm running a simulation with rtrace, where I've set -I to compute
irradiance rather than radiance values.

Though reading the man pages, I do find the explanations of the flags
somewhat confusing:



Boolean switch to compute irradiance rather than radiance values. This
only affects the final result, substituting a Lambertian surface and
multiplying the radiance by pi. Glass and other transparent surfaces are
ignored during this stage. Light sources still appear with their
original radiance values, though the -dv option (below) may be used to
override this. This option is especially useful in conjunction with
ximage (1) for computing illuminance at scene points. 



Boolean switch to compute irradiance rather than radiance, with the
input origin and direction interpreted instead as measurement point and


In what cases should one use the -i flag and in which cases is -I the
preferred option?

I find it hard to make the distinction from the docs.






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