[Sidefx-houdini-list] Linear workflow

Matt Estela matt.estela at gmail.com
Thu Mar 3 07:57:37 EST 2016


You haven't provided enough information to say definitively 'yes' or 'no'.

A 3d lut can be baked down to a 1D lut that mplay can use, again Aces
provides tools to do this (there might even be a lut baker that ships with
houdini, its been a while since I looked).

Anyway, it sounds like you're not going to get much help from your
co-workers or the client, so the only thing you can do is test. Get the
compers to write you out a linear exr of something, that they can load back
into nuke, view through the lut, confirm it looks as expected.

Take that into houdini, make a shader that loads the exr and feeds it
directly to Cf. Assign that shader to a plane, render out an exr, view that
in nuke. Ideally, it should look identical to the original image. If you
can get a 1D lut baked for you, it should look identical in the render view
and mplay too.

If that all checks out, then try more ambitious tests of overexposed and
underexposed images, run them out of nuke, into houdini, back to nuke, you
shouldn't see any change.

If you can't get a lut to use in houdini, then you'll have to just struggle
as best you can by adjusting the colour correction values in the render
view so that they match as close as possible to the nuke lut. Beyond that,
you'll have to just accept you're working in a non-look-lut space, and
frequently write out exrs to load in nuke to confirm you're staying on
track.





On 3 March 2016 at 10:24, François Duchesneau <sidefx at trinix.ca> wrote:

> And then based on this new information I added, would the answer still be
> yes?
>
> Thanks again guys
>
> Francois
>
>
> On 03/02/2016 09:01 AM, François Duchesneau wrote:
>
>> I don't think this lut is for a particular monitor color space because we
>> use it only for a certain project. Actually, some shots within the projects
>> don't use any LUT and we look at our renders with 2.2 gamma in mPlay.
>>
>> It is a 3D LUT provided by the client used to visualize their plates that
>> behaves similar to the second case you described. They advised me to make a
>> color correction in Nuke per channel on the HDRI to make things look right
>> when I light.
>>
>> In fact yesterday somebody told me Houdini doesn't allow 3D LUT so what
>> we're looking in mPlay is not even right.
>>
>> Francois
>>
>> On 03/02/2016 02:02 AM, Matt Estela wrote:
>>
>>> Depends. :)
>>>
>>> If the lut you're using has taken linear into consideration, (eg, you're
>>> using an aces colour pipeline, and the person in charge has made you a
>>> lut
>>> for mplay that does scene linear -> monitor conversion), yes.
>>>
>>> If it's some random lut created by the DOP/grading department to make the
>>> highlights vaguely green, mids a delicious purple and crush the blacks a
>>> little (ie, its a look LUT), the answer is probably no.
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