Shuffle Node

[Daniel Davie]

Hey guys,

We have just started switching a bunch of our QC compositing tasks from Nuke to Gaffer and so far it has been awesome! 

I have run into a small issue with the Shuffle node however. I am using it to shuffle out the alpha of our shadow passes to RGB so that we can QC them and this work fine when I am working in the UI but when I try and run it headless on the farm I get the error:

KeyError: "'channel' is not a child of 'channels'"

I am trying to set the value using the following code which works perfectly when run in the script editor of the UI:

root["<nameOfTheNode>"]["channels"]["channel"]["in"].setValue("A")

root["<nameOfTheNode>"]["channels"]["channel1"]["in"].setValue("A")

root["<nameOfTheNode>"]["channels"]["channe2"]["in"].setValue("A")

root["<nameOfTheNode>"]["channels"]["channe3"]["in"].setValue("A")

Also when I open up the Gaffer script that was created on the farm the node editor is empty when I have the shuffle node selected. Is there something I am doing wrong?

Thanks and all the best,

Dan

[EzequielM]

When you create a Shufle node through python it will be created without the channels plug

GafferImage.Shuffle( "Shuffle" )

Make sure your channel, channel1, channel2, and channel3 plugs exist before setting their value

You can create them like this

__children["Shuffle"]["channels"].addChild( GafferImage.Shuffle.ChannelPlug( "channel", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )

__children["Shuffle"]["channels"].addChild( GafferImage.Shuffle.ChannelPlug( "channel1", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )

__children["Shuffle"]["channels"].addChild( GafferImage.Shuffle.ChannelPlug( "channel2", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, ) )

__children["Shuffle"]["channels"].addChild( GafferImage.Shuffle.ChannelPlug( "channel3", flags = Gaffer.Plug.Flags.Default | Gaffer.Plug.Flags.Dynamic, )

www.ezequielm.com

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Ezequiel Mastrasso

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+353 83 0030034

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[Daniel Davie]

That worked a charm, thank you Ezequiel!

Dan

[Carlo Giesa]

Hi there!

I'm wondering, if we can control the "channels" plug via python expressions. I'm trying to build a contact sheet setup that extracts all layers from a multi layer exr file. Or would it be better to approach this via OSL? By the way, I started from the provided contact sheet example that is still using the "Loop" node which doesn't seem to be accessible anymore in recent versions of Gaffer. Might there be other approaches? I tried to see if a "CollectImages" node could do the trick, but I don't see how to use to in that case, since from my understanding, the collect node does create a new layer inside the image file, which is not what I want.

Greets,
Carlo

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[Carlo Giesa]

Ok, I managed to handle the dynamic channel selection with the OSLInLayer node. Still wondering, if I should replace the "Loop" setup with something else. With a lot of AOVs, still is taking a bit of computation time to get a full contact sheet.

Greets,
Carlo

[Murray Stevenson]

Hey Carlo!

You could use an expression to set the values of the `in` and/or `out` child plugs of each ChannelPlug added to a Shuffle. I’ve attached a basic example using some ContextVariables nodes to control which layer gets shuffled to RGBA.

Short of writing a dedicated C++ ContactSheet node, the Loop approach is likely your best option at present...

Cheers,

Murray

[Carlo Giesa]

Hey Murray!

Thanks for the example, that is working like a charm.

Although, I wasn't able to run this contact sheet loop setup on a merged EXR with 81 AOVs inside. I let it run for one hour for a single frame and nothing happened. It worked great with an EXR of 19 AOVs. Not sure if that is a limitation due to the loop setup. I finally put something together using only OpenImageIO.

Greets,

Carlo

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