I'm pretty sure it did it output those values out of the box, but I'm not sure if it changes across prman versions.
On Thu, Apr 28, 2011 at 3:11 PM, Ivan Busquets <[email protected]>wrote: > exr/screenWindowWidth is calculated by the display driver the same way I > described, so yes, it should give the same result. > > However, I was not sure whether exr/screenWindowWidth is standard for all > versions of the prman exr display driver. > > > > > On Thu, Apr 28, 2011 at 2:22 PM, [email protected] < > [email protected]> wrote: > >> I think I remember also doing it like this with the default prman >> metadata. >> >> H_aperture=node.metadata('exr/screenWindowWidth', frame_numb) >> V_aperture=H_aperture/Aspect >> >> >> On Thu, Apr 28, 2011 at 1:29 PM, Ivan Busquets <[email protected]>wrote: >> >>> The projection matrix from prman only stores a FOV, or the relationship >>> between focal-length and horizontal aperture. >>> If you want the "real" focal length values, you will need to know the >>> size of your filmback. >>> >>> If you don't care about the "real" focal length value, you can still get >>> the right projection values by setting the focal length to 1, and getting >>> the filmback size like this (proj_matrix is a Matrix4 object filled from the >>> exr/worldToNDC metadata key): >>> >>> lx = (-1 - proj_matrix[12] - proj_matrix[8]) / proj_matrix[0] >>> by = (-1 - proj_matrix[13] - proj_matrix[9]) / proj_matrix[5] >>> rx = (1 - proj_matrix[12] - proj_matrix[8]) / proj_matrix[0] >>> ty = (1 - proj_matrix[13] - proj_matrix[9]) / proj_matrix[5] >>> >>> swW = max( lx , rx ) - min( lx , rx ) # Screen Window Width >>> swH = max( by , ty ) - min( by , ty ) # Screen Window Height >>> >>> If you have access to the real filmback size (either from custom metadata >>> or because you can assume you'll always be dealing with cameras that have >>> the same filmback size), you could then get a "real" focal length value from >>> filmBack.width / swW. >>> >>> Hope that helps. >>> >>> Cheers, >>> Ivan >>> >>> >>> 2011/4/28 Lucien Fostier <[email protected]> >>> >>>> Hi fellow tds >>>> >>>> I m trying to create a camera from exr metadata coming from prman. >>>> >>>> So i use the projection matrix world to camera which give me position >>>> and orientation in space. >>>> >>>> Id like to extract the focal lenght from this data but i cant find how >>>> to do it. >>>> >>>> May someone help me about this or give me some pointer? >>>> >>>> Thanks >>>> >>>> Lucien >>>> >>>> Envoyé de mon iPhone_______________________________________________ >>>> Nuke-python mailing list >>>> [email protected] >>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-python >>>> >>> >>> >>> _______________________________________________ >>> Nuke-python mailing list >>> [email protected] >>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-python >>> >>> >> >> _______________________________________________ >> Nuke-python mailing list >> [email protected] >> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-python >> >> > > _______________________________________________ > Nuke-python mailing list > [email protected] > http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-python > >
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