Precomp after Interactive Render into a Catalogue

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Nico Rehberg

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Jul 3, 2024, 4:34:39 AMJul 3
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Hi,

I'm trying to do a little precomp onto the plate during interactive rendering. At the moment I use the output of the catalogue to do that. Here's a simple example.
ksnip_20240703-102725.jpg
This has the drawback that the catalogue does not store the precomped images, so when I try to switch or compare between shots the old rendering is overlayed over the wrong plate. Is there a way to build this to have the catalogue at the end? Read the interactive render directly into the grade?
Another small nuisance is that when I look at the precomp (a merge) node in the viewer I do not get the small Start and Stop buttons to drive the renderer I would get when I look at the catalogue.

Thanks,
Nico

John Haddon

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Jul 4, 2024, 4:50:04 AMJul 4
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Hi Nico,

 Is there a way to build this to have the catalogue at the end? Read the interactive render directly into the grade?

Not really - the Catalogue is the expected way to receive interactive renders. But there are a few other possibilities that might be worth considering :
  • You can middle drag an image node from the GraphEditor into the image listing for the Catalogue, to snapshot the current output of that node as a new image in the Catalogue. So you could drag `Precomp` into the Catalogue at any time to take a copy of it. You could potentially automate this so that it happened every time you stopped a render.
  • Every rendered image contains `gaffer:context:<name>` metadata for the context it was rendered in. You could query that from the output of the catalogue, and use it to have the ImagePlaneReader automatically load the right plate for that context. So as you switched between images in the Catalogue, the ImagePlaneReader would automatically switch too.
  • Not particularly relevant to your problem, but if you don't know already, it's worth knowing that the Viewer has a built-in capability to compare images, including to overlay one on another. This is much faster than using a Merge node, and is the preferred way of displaying a render over a plate. There are some further details here : https://blog.gafferhq.org/?p=1061
Another small nuisance is that when I look at the precomp (a merge) node in the viewer I do not get the small Start and Stop buttons to drive the renderer I would get when I look at the catalogue.

We use `gaffer:sourceScene` metadata in the image to determine if it was rendered from a node in Gaffer, and display the Start/Stop buttons. This will be lost by the Merge node, which passes through the metadata from the first input only. You can switch the inputs round and use `Under` as the merge mode, or you could use CopyImageMetadata to copy the metadata back in below the Merge.

Hope that helps...
Cheers...
John

Nico Rehberg

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Jul 10, 2024, 8:16:37 AMJul 10
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Thanks again John for the in-depth explanation. That's a lot of valuable information. The metadata trick was easy to implement and already helps.

Cheers,
Nico
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