Cannot set plug except during computation

[Carlo Giesa]

Hi there!

I have a little issue that I'm not entirely sure how to fix. To load caches into our Gaffer scenes, we have a model reader which is basically a custom node that contains a scene reader. On our custom node, we add a string plug that we connect as input to the scene reader's 'fileName' plug.

Sometimes (I could not yet exactly figure out when exactly), when setting my '__path' plug to update the cache path, I get following error:

IECore.Exception : line 2 : Cannot set value for plug "gui.scripts.ScriptNode5.SceneReader.fileName" except during computation.

I actually can reproduce this very easily with a box node containing a SceneReader and a custom string plug on the box node that is connected to the scene reader's 'fileName' plug.

Any idea how I can 'fix' this? I also have the impression that this is a recent issue that we didn't have before (currently, we are using Gaffer 1.6.5.1).

Thanks for any input!

Greets,
Carlo

[Carlo Giesa]

Ah sorry, I just realize that I can't reproduce the error with the box (wrong test code). But I have the impression that this might be related to incoming connections, however, my __path plug doesn't have any incoming connection. I continue to search...

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[Carlo Giesa]

Mmmh, looks like some 'corrupted' node setup on our side. Not really sure how we got there. Sorry for the noise. :)

[Daniel Dresser]

That exception would indicate that you're trying to explicitly set a plug that is driven by something else. For example, I think this is what you would get if you tried to set the value of the fileName of a SceneReader inside a box while the fileName plug is driven from an input on the box. Just mentioning in case it helps you reconstruct what might have gone wrong ( your error message suggests that the SceneReader wasn't inside the box when the error happened, but maybe it was somehow connected to something, or keyframed. )

-Daniel

[Carlo Giesa]

Hi Daniel!

Thanks for your feedback. Yes, I was indeed mixing up things here. Sorry for that.

However, I could not yet really figure out what went wrong initially. In the meantime, things seem to work as expected. Let's see for how long. :)

Greets,

Carlo

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