[Radiance-general] Zenith Luminance from rvu

[Vaib]

Hello Everyone,

I am trying to create falsecolor fish-eye image of just the sky. For that I
am using:

rpict -vta -vp 0 0 0 -vd 0 0 1 -vu 0 1 0 -vh 180 -vv 180 sky.oct |
falsecolor -s XYZ -l cd/m2 > sky.hdr

Dr.Mardaljevic in his dissertation said to set -s argument of falsecolor
close to the Zenith luminance, that can be obtained by rvu's trace command.

To get the Zenith luminance, I am tracing the ray (using rvu) that is
approximately at the centre of the image created with the above view
parameters, and setting this ray's luminance value as the -s option of
falsecolor.

Is this the right way to show/cover the whole luminance spectrum in the sky
? (It doesn't look so in the image..)

Or shall I trace the ray at the apparently at the brightest pixel ? (by
reducing the exposure, and figuring out that pixel)

I think the term Zenith Luminance may mean the luminance at the centre of
the sky, but I must take your opinion before concluding. Thank you!

Best regards,
Vaib
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