Re: [Openexr-devel] Multipart backward compatibility?

[Piotr Stanczyk]

Hi Dalai, 

Generally speaking ... 

If you want backward compatibility, then you have no choice but to use the older, multi-view API.

If you don't have those restrictions, or you wish to give your users the choice, then you can experiment with the multipart approach. That, as Gonzalo mentioned, will give you better performance if you are seeking to access just one of the views.

The over-riding principle that guided the v2.0 development was that if you use nothing but 1.X APIs then you will get an image that existing readers can recognise and read correctly. (Indeed, the image should be identical for the most part). 

Using v2.X API calls will result in an image that is not backward compatible, hence the issues with exrdisplay that you outlined above. 

I hope that helps somewhat. 

Piotr

On 12 September 2014 08:03, Dalai Felinto <address@hidden> wrote:

Hi Gonzalo,

> This beats the purpose of multipart files. The idea of multipart files is that it gives you fast random access to any layer. It is used in stereo but not only in stereo.

Yup, and yet this (singlepart) is the default we get out of
exrmultiview and what all the openexr-images sample files use. I know
multipart is not something exclusive to multiview, but the docs seemed
to indicate multipart as the preferable approach for multiview files.

Given that multipart also provides a faster access I would rather
favour it over singlepart, but backward incompatibility may be a no
go. (thus the email to get a clear picture of that).

Thanks,
Dalai

--
blendernetwork.org/dalai-felinto
www.dalaifelinto.com

2014-09-12 16:34 GMT+02:00 Gonzalo Garramuno <address@hidden>:
> On 12/09/14 07:58, Dalai Felinto wrote:
>>
>> Hi there,
>>
>> I'm working in supporting a multiview pipeline in Blender, and part of
>> this involves supporting OpenEXR multiview format. I'm currently
>> wondering what is the best option to save the images with the most
>> backward compatibility.
>>
>> At first I considered dumping the data in a single-part file:
>>
>> R
>> G
>> B
>> A
>> right.R
>> right.G
>> right.B
>> right.A
>
> This beats the purpose of multipart files.  The idea of multipart files is
> that it gives you fast random access to any layer. It is used in stereo but
> not only in stereo.
>

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