Re: Anyone knows how maya computes filmback translation?

[Philipp Oeser <philipp.oeser(at)liga01.de>]

Hi,
thanx again for your suggestions.
There is little time to really nail this down, for now I'll just 
normalize as Brent suggested
and put in a slider in the exporter to manually tweak the "magic 
factor", which seems to be around 2
(2 exactly doesnt give me pixel-precission for some reason)

Well, thanx again
Philipp

Tim Leydecker schrieb:
> An extra shot in the blue, at least for testing purposes,
> make sure you have identical settings for outputresolution
> and pixelaspectratio set in both Maya and XSI, otherwise
> Maya may give you unexpected results, f.e. when you have
> specified 640x480px in the RG but a 16:9 camera format,
> you´ll get your cameraoutput "squeezed" into the 4:3 render.
>
> Could be one of the reasons for misalignements, another is
> the optical center shift (e.g. "pseudo shift lens"), I´m not sure
> wether Maya supports this feature - architectural renderings?
>
> Up until now I helped myself by setting the filmbacksize to the
> aspectratio, e.g. a 16:9 format would be 1.778:1 (inch) in Maya
> and XSI, 768x432/1024x576/1280x720/1920x1280 (square px)
> as (preview)resolutions, I was able to mix renderings with these
> settings and a camera exported via *.xsi between Maya and XSI.
> I´ll usually leave shifts untouched but use 21-75 (pseudoMM) lenses,
> where a 50 (pseudo mm) lens pretty much equals the "normal viewing".
>
> I´ve never tried to match to real footage, thought...
>
> Cheers
>
> tim
>
>
> ----- Original Message ----- From: "Brent McPherson" 
> <brentmc(at)Softimage.COM>
> To: <XSI(at)Softimage.COM>
> Sent: Monday, December 04, 2006 2:56 PM
> Subject: RE: Anyone knows how maya computes filmback translation?
>
>
> > Hi Philipp,
> >
> > I don't have Maya to compare with but in tech-speak a normalized value
> > is a value between 0 and 1. So if you want to produce a normalized value
> > > from the XSI settings you would take the horizontal offset and 
> > > divide by
> > the filmback width like this:
> >
> > -0.0307 / 0.9802 = -0.0313
> >
> > Now, based on your guesstimate in Maya of -0.065 it looks like there is
> > a scale factor of 2 in there so I would expect the equivalent Maya value
> > to be:
> >
> > -0.0313 x 2 = -0.0626
> >
> > (and to go from Maya to XSI just take the normalized value, divide by
> > two
> > and finally multiply by the filmback width)
> >
> > Of course this is just a guess on my part but you should be able to
> > verify whether this is the case by running a few different settings
> > through both XSI and Maya.
> >
> > Hope this helps.
> > --
> > Brent
> >
> > -----Original Message-----
> > From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf
> > Of Philipp Oeser
> > Sent: Sunday, December 03, 2006 4:22 AM
> > To: XSI(at)Softimage.COM
> > Subject: Anyone knows how maya computes filmback translation?
> >
> > Hi everyone,
> > I need to convert a XSI camera to Maya and I just cant figure out how
> > maya computes the translation on the filmback. (their docs say "The
> > values are normalized with respect to viewing area").
> > An example:
> > I have a 0,9802 inch x 0,7352 inch filmback in XSI with an -0,0307 inch
> > horizontal filmback translation/optical center shift (here it is all in
> > inches)
> > The cam in Maya (same filmback of 0,9802 inch x 0,7352 inch) seems to
> > match at a Filmback translate H with a value of about -0.065. (All other
> >
> > settings in Filmback are standard, no scaling, no filmoffset, no
> > lenssqueeze) (and matching also seems to be dependent on overscan).
> > Sorry, it's late at night and I cant get it right...
> >
> > Any ideas?
> > Thanx in advance
> > Philipp
> >
> > --
> >
> > Philipp Oeser
> > Liga_01 Computerfilm GmbH
> > www.liga01.de
> >
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--

Philipp Oeser
Liga_01 Computerfilm GmbH
www.liga01.de


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