[Radiance-general] rtrace -i -I flags

[Giulio Antonutto]

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...

G.

 

 

 

 

________________________________

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

 

Hi,

 

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:

 

-i 

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. 

 

-I 

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

 

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.

 

Thanks,

 

-jelle 

 

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