[Radiance-general] Mapping from hemisphere projection to latitude-longitude format

[Thomas Bleicher]

Claus.

I used ImageMagick to convert from fisheye to rectangular projections.
I wasn't much concerned with the accuracy so I can't tell if it's
appropriate for you. You can find more here:

http://www.fmwconcepts.com/imagemagick/index.php

http://www.fmwconcepts.com/imagemagick/polar/index.php

I also remember that I used one of the Radiance binaries to convert
from one projection to another. I can't remember which tool it was and
which conversions are possible. If you use a non-Radiance source image
you have to convert it to Radiance hdr format and add the view
specification to allow the conversion.

Regards,
Thomas

On Mon, Dec 7, 2009 at 12:41 PM, Claus B. Madsen <cbm at imi.aau.dk> wrote:
>
>
>
> Dear list members,
>
> I use HDRShop to convert between mappings for environment maps, e.g., from
> mirror ball to lat-long, etc.
>
> I now have two other mappings that I wish to convert to lat-long (though I
> realize that both mappings will only give me half a sphere, e.g., top half
> of lat-long map).
>
> 1) An image taken with a Sigma 8mm 180 degree field-of-view fish eye lens to
> take a high-res image of the sky (same hemispherical mapping as RADIANCE
> renders into when using the -vth option for rview/rpict)
>
> 2) An image of a diffuse hemi-sphere (diameter of 0.3 meters, turned out on
> a lathe) spray painted with a diffuse grey
>
>
> I am convinced that both mappings are identical (i.e. identical to the
> hemi-spherical projection model in RADIANCE). So far I have used the
> 'mirrorball closeup' format in HDRShop but found this to be the wrong
> mapping yielding incorrect lat-long mappings. I have now understood the
> entire geometrical issue and just need a piece of software to warp
> hemisphere images to lat-longs ... perhaps a plugin for HDRShop?
>
> A couple of years ago I raised this issue with the people who wrote HDRShop
> but they claimed the Sigma lens should be treated as mirror ball closeup
> when re-mapping in HDRShop. I am now convinced this is not true after having
> tested it  extensively.
>
> Sincerely,
> Claus
>
>
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