They're all slightly different, and there are multiple variations of
some extensions (e.g I've seen about 3 variations of .3dl with different
shaper-LUT support..)
Of the ones you list, most support a prelut to some degree. CSP has a
spline-based prelut, cms has a linearly sampled 1D LUT, vf has an
pretransform matrix, blut has linear-or-log sampled 1D LUT and simple
range-remapping/scaling controls, and so on (could be wrong about some
of them)
Since few (none?) of the LUT formats are well documented, I normally
rely on OCIO's FileFormat*.csp files in
https://github.com/imageworks/OpenColorIO/tree/master/src/core
The readers are "mostly correct", in so much as they are
reverse-engineered from example LUT's and the results compared against
existing implementations (e.g the .look format was tested against IRIDAS
Speedgrade)
There's also a summary on
http://opencolorio.org/FAQ.html#what-lut-formats-are-supported
..but it's not particularly comprehensive, yet
On 16/01/13 11:18, Dan Rosen wrote:
Cool. Thanks Ben. This makes sense. Do all those LUT file-types, besides
3dl actually carry a 1D shaper LUT? I thought only .csp and .blut do,
but I see that in the GenerateLUT node it refers to 1D preLUT in blut,
cms, csp, cub, cube and vf.
On Tue, Jan 15, 2013 at 3:33 PM, Ben Dickson <[email protected]
<mailto:[email protected]>> wrote:
The GenerateLUT node does not have any way to specify the pre-LUT
part of the CSP file, the "1D preLUT" options only apply to certain
output formats (e.g .cms)
In the past I've used the GenerateLUT to create the 3D part of the
LUT, then added in the preLUT section manually (with a Python script)
Not exactly what you need, but this should give you the basic idea:
https://gist.github.com/__4543134 <https://gist.github.com/4543134>
This only samples the ColorLookup between 0-1, and it writes a 1D
CSP file (which has an identical prelut section)
> I'm not sure if the Nuke node requires that I have a config.ocio file
Nope, the current GenerateLUT node pre-dates the OCIO integration.
If you have an suitable config, you can use OCIO's ociobakelut command,
http://opencolorio.org/__userguide/baking_luts.html
<http://opencolorio.org/userguide/baking_luts.html>
This can write a preLUT allowing linear input
It would be nice if OCIO had it's own OCIOGenerateLUT node, there's
a ticket for this:
https://github.com/imageworks/__OpenColorIO/issues/8
<https://github.com/imageworks/OpenColorIO/issues/8>
On 16/01/13 06:55, Dan Rosen wrote:
Hello,
I am trying to use GenerateLUT to author csp files for linear light
images to display conversion. We also have a custom LogLin so
I'd like
to set the shaper lut to something custom with a file or values
there.
I'm not sure if the Nuke node requires that I have a config.ocio
file or
not, but I cannot seem to figure it out. I've looked in the docs and
don't see it there either. Any help is much appreciated.
Thanks,
Dan
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