[Radiance-general] sky mapping

[Giovanni Betti]

Lars,
Thanks a lot for this,
It seems to work although in a slightly modified version (rx +90)
The results are much closer in the central part of the image (I assume
the difference is only because of interpolation or anti aliasing
effects...)And the brightest band at the horizon has almost disappeared
(although not entirely... again is the anti aliasing to blame?)
I've also noticed that for this process to work it is crucial that the
original sky image has a normalized exposure (1) otherwise all the
values are scaled down...

Thanks again,

Giovanni

-----Original Message-----
From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org] On Behalf Of Lars
O. Grobe
Sent: 09 September 2009 02:44
To: Radiance general discussion
Subject: RE: [Radiance-general] sky mapping

Hi Giovanni,

I have used fisheye.cal, which comes with radiance. I also used the
angular fisheye with the vta-view, as you did. The only important point
was to translate the mapping, as fisheye.cal expected the image center
to be +y (north in most models), while for sky capturing you point up.

The mapping for me is

void colorpict skyhdrmapping
11 red green blue sky.hdr fisheye.cal fish_u fish_v -rx -90 -rz 180
0
0

And sky.hdr has the north on the top when seen as a 2d image.

I am not sure whether Peter's cal-file does any more advanced stuff
related to his fisheye - it could be that he is correcting for some
vignetting stuff that does not exist in you synthetic image. That would
explain the higher pixel values close to the edge.

Cheers,

Lars.


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