[Sidefx-houdini-list] Cam back to aperture Maya/Nuke/Houdini

Peter Bowmar pbowmar at gmail.com
Fri Sep 24 19:33:02 EDT 2010


Thanks guys, it turns out that it's mostly FBX not putting all data
into the FBX file, or Houdini's importer not reading it (haven't
figured that one out yet) but when you import FBX it doesn't set the
cam res and that of course screws up the aspect ratio. Problem sorted!

Cheers,

Peter B

On 24 September 2010 16:12, Andrew D Lyons <tstexture at gmail.com> wrote:
> Houdini's camera is fine. It uses identical values to Nuke and plays well
> with prman as well. Maya is the odd one out from that group. That thing is a
> nasty piece of work. Just pray people are using the horizontal fit. It gets
> more nasty otherwise. In any case it sounds like your problem is in the FBX
> exporter for Houdini (SESI!?). If you really need to go from Houdini to Nuke
> a lot you may be better off not using FBX and just going direct from Houdini
> to Nuke. It's not that hard to do the string formatting involved in that
> converter.
>
> I should point out that getting soho to match the maya FOV is another drama
> that most converters miss - but is essential if renderer integration with
> perfect registration is a goal. This is how Maya does it:
>
> proc float AEcalculateFOV( string $focalStr, string $horStr )
> {
>    float $focal = `getAttr $focalStr`;
>    float $aperture = `getAttr $horStr`;
>
>    float $fov = (0.5 * $aperture) / ($focal * 0.03937); // mm2inch rounded
> down arbitrarily
>    $fov = 2.0 * atan ($fov);
>    $fov = 57.29578 * $fov;
>
>    return $fov;
> }
>
> You can hopefully reverse engineer the soho fov code needed to match that.
> It's kind of nasty. You have to use the houdini focal and aperture settings
> to reverse engineer the focal that maya uses with the approximate values of
> mm2 inch etc, and then use that slightly wrong focal instead of the original
> clean Houdini focal. It does give perfect registration with Maya renders
> though. SESI don't ship that hack with FBX or soho, and I haven't seen it
> mentioned on the web anywhere...
>
> Cheers
>
>
> On 24 September 2010 15:57, Ron Schab <ron.schab at gmail.com> wrote:
>
>> Hi Peter,
>>
>> I remember Miles had a Houdini-Maya camera exchange tool on his site.
>> I haven't had the chance to try it myself but as I know Miles it's gonna be
>> solid.
>> It might not be the "all around" solution for you as it doesn't seem to
>> support Nuke out of the box, but it should get you around the problems you
>> are facing.
>>
>> www.houdinistuff.com
>>
>> and maybe this is of interest for you too:
>>
>> http://animbyu.groups.et.byu.net/wiki/index.php?title=Houdini_and_Maya
>>
>>
>>
>> hope it helps
>> cheers
>> Ron
>>
>>
>> Ron Schab
>> -----------------------------------------------------------------------
>>
>> http://www.linkedin.com/in/ronschab
>>
>> http://www.xing.com/profile/ron_schab
>> http://www.xing.com/go/invita/4525868
>>
>> GER:+49 (0)1577 - 4096084
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>>
>>
>> On Sat, Sep 25, 2010 at 08:19, Peter Bowmar <pbowmar at gmail.com> wrote:
>>
>> > Hi,
>> >
>> > Anyone dealt with this? Any pointers appreciated! I sure wish
>> > Houdini's camera was compatible with the rest of the world :(
>> >
>> > Here is the problem we are seeing.  When a camera is sent via FBX from
>> > maya to Houdini the filmback
>> > values are changed to an aperture value.
>> > Then when the camera is exported via FBX from Houdini to Nuke or back
>> > to Maya the values are
>> > different.
>> >
>> > Below are the numbers we are using/seeing:
>> >
>> >
>> > Actual filmback:
>> > 0.882" (22.4mm) x 0.496" (12.598mm)
>> >
>> > Image resolution:
>> > 1920x1080
>> >
>> >
>> > Maya to Nuke is good
>> >
>> > Maya to Houdini:
>> > Houdini converts the filmback values to 16.7979 (aperture)
>> >
>> > Houdini to Nuke = different values: 0.661" x 0.372
>> > Houdini back to Maya = 0.661 x 0.372
>> >
>> > Cheers,
>> > --
>> > No, I am not on Facebook.
>> > _______________________________________________
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>> >
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>
>
>
> --
> =======================================
> Andrew D Lyons | Digital Artist | http://www.tstex.com
> =======================================
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