Re: Unit scale for Z values

Just thinking out loud...

Does it make sense to have something akin to RFC for such things as part 
of the VFX Platform (i.e. VFX RFC) as a way to get everyone on the same 
page so that even if it is a multi-year process, things don't get lost 
along the way as people change projects, companies etc.

Cheers

On 2016-01-15 1:56 PM, Jason Iversen wrote:
> Yeah, I do realise that asking the library itself to do this is a 
> rather big responsibility and it might pose more questions than it 
> answers. What I was hoping to avoid is the giant process of 
> recommending a standard metadata key, and then requesting 3rd party 
> vendors to respect this key upon write and do the thing upon read - 
> which you may appreciate could be a multi-year process with spotty 
> coverage all the way. I was hoping to get the issue addressed at the 
> source.
>
> Thanks,
> Jason
>
>
> On Thu, Jan 14, 2016 at 4:19 PM, Larry Gritz <[email protected] 
> <mailto:[email protected]>> wrote:
>
>     OIIO 1.6.9 has the -mulc command, but it doesn't work properly
>     with deep images -- that was fixed/added (um, now that you mention
>     it, likely at your request) to the master at the time when I was
>     trying to freeze 1.6 for a release. It seems to be working and
>     safe, so I'll backport it to 1.6, in case it's helpful.
>
>     Seems to me that making the IlmImf library itself try to be too
>     smart about unit conversion and scale things under the covers
>     might create as many problems as it solves, but I think it's a
>     really good suggestion for apps (like Houdini or Maya) to apply a
>     scale when writing depth channels -- after all, they know what
>     units they are computing in.
>
>     Another thing that may be good practice is to recommend a
>     particular metadata name that reveals what units the depths are in
>     ("DepthUnit" -> "meter" or whatever) and then presumably a really
>     smart Nuke deep merge node might apply appropriate scales to make
>     sure the operand images are in the same space, if they both have
>     documented units but don't match.
>
>     -- lg
>
>
>>     On Jan 14, 2016, at 4:02 PM, Jason Iversen <[email protected]
>>     <mailto:[email protected]>> wrote:
>>
>>     Hi Larry,
>>
>>     Thanks, and yes - I was one of the people who at least chorused
>>     with the request to be able to apply a z-scale within oiiotool. 
>>     We just installed 1.6.9 here; does that have the -mulc feature?
>>
>>     My question is definitely aimed at the idea of support for
>>     automatic conformance to try to aid interchange without incurring
>>     pipelining - ie, tracking of originating scale and destination
>>     scale, and generating intermediates.
>>
>>     Thanks,
>>     Jason
>>
>>     PS.  I have the same question poised for Alembic :)
>>
>>
>>
>>
>>     On Thu, Jan 14, 2016 at 11:13 AM, Larry Gritz <[email protected]
>>     <mailto:[email protected]>> wrote:
>>
>>         I'm not sure if this addresses your question directly (which
>>         seemed to be more about automatic conformance to a unit scale
>>         upon read/write?), but as far as converting the values of a
>>         deep file that already exists:
>>
>>         If you know that the z's are in decimeters and you want to
>>         convert to meters, and you know the channels of the file
>>         (let's say that you know that there are two channels, "A" and
>>         "Z"), you can do
>>
>>             oiiotool decimeters.exr -mulc 1.0,10.0 -o meters.exr
>>
>>         Basically just multiplying every alpha value by 1.0 (keeping
>>         it the same) and multiplying every Z value by 10.0
>>         (converting decimeters to meters).
>>
>>         Sorry, I just checked and the deep support for "-mulc" is a
>>         recent addition, at this moment is in the "master" branch
>>         only. But I can backport it to a stable release branch if
>>         people need it.
>>
>>
>>         > On Jan 13, 2016, at 12:27 PM, Jason Iversen
>>         <[email protected] <mailto:[email protected]>> wrote:
>>         >
>>         > Hi all,
>>         >
>>         > Is there any mechanism in place, or planned, or
>>         rejected(!), for adjusting (deep) Z values to match a unit
>>         scale? In environments where you interchange deep EXR2's
>>         between packages which are working in different unit scales
>>         (eg. Maya in decimeters and Houdini in meters) you would want
>>         to convert to the unit scale to the hosted application upon
>>         read. I'd imagine you'd do this be comparing it to a
>>         unit-scale stored in metadata.
>>         >
>>         > Regards,
>>         > Jason
>>         >
>>         >
>>         > --
>>         > Jason Iversen
>>         >   Production Technology Supervisor
>>         >     Digital Domain
>>         >
>>
>>         --
>>         Larry Gritz
>>         [email protected] <mailto:[email protected]>
>>
>>
>>
>>
>>
>>     -- 
>>     Jason Iversen
>>       Production Technology Supervisor
>>         Digital Domain
>
>     --
>     Larry Gritz
>     [email protected] <mailto:[email protected]>
>
>
>
>
>
> -- 
> Jason Iversen
>   Production Technology Supervisor
>     Digital Domain
>
>
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-- 
Nicholas Yue
Graphics - Arnold, Alembic, RenderMan, OpenGL, HDF5
Custom Dev - C++ porting, OSX, Linux, Windows
https://ca.linkedin.com/in/nicholasyue
https://vimeo.com/channels/naiadtools

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