Sorry, no benchmarks yet.  I started making a doc about exr to put up on
nukepedia that one day I will finish.

Ryan: are the exr files scanline or tile exr's?

-deke


On Thu, Sep 1, 2011 at 14:18, Dan Walker <[email protected]> wrote:

> Hey Deke,
>
> Could you elaborate on the last paragraph. Given a multi chan EXR.  Are
> there bench mark tests that have been done to track optimal setups in comps?
> Basically, better to do this than that.  I know there are a multitude of
> scenarios you have to consider but there are some tips users can supply
> based on their experiences.
>
> I'd say submitting them in an email thread is probably the best approach or
> the Foundry can compile and validate the submitted tips.  They're not busy
> working on anything at the moment, right?! ;-)
>
>
>
>
> On Thu, Sep 1, 2011 at 1:55 PM, Deke Kincaid <[email protected]>wrote:
>
>> Exr files are interleaved.  So when you look at some scanlines, you need
>> to read in every single channel in the EXR from those scanlines even if you
>> only need one of them.  So if you have a multichannel file with 40 channels
>> but you only use rgba and one or two matte channels, then your going to
>> incur a large hit.
>>
>> Another thing is it sounds like you are shuffling out the channels to the
>> rgb before you merge them.  This also does quite a hit in speed.  It is far
>> faster to merge and pick the channels you need rather then shuffling them
>> out first.
>>
>> -deke
>>
>> On Thu, Sep 1, 2011 at 12:37, Ryan O'Phelan <[email protected]>wrote:
>>
>>> Recently I've been trying to evaluate the load of nuke renders on our
>>> file server, and ran a few tests comparing multichannel vs. non-multichannel
>>> reads, and my initial test results were opposite of what I was expecting.
>>> My tests showed that multichannel comps rendered about 20-25% slower, and
>>> made about 25% more load on the server in terms of disk reads. I was
>>> expecting the opposite, since there are fewer files being called with
>>> multichannel reads.
>>>
>>> For what it's worth, all reads were zip1 compressed EXRs and I tested
>>> real comps, as well as extremely simplified comps where the multichannel
>>> files were branched and then fed into a contact sheet. I was monitoring
>>> performance using the performance monitor on the file server using only 20
>>> nodes and with almost nobody using the server.
>>>
>>> Can anyone explain this? Or am I wrong and need to redo these tests?
>>>
>>> Thanks,
>>> Ryan
>>>
>>>
>>>
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>>
>>
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>
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