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Compositions and 'External Control of Position Scale & Rotation' option


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Not sure if this is a bug or a feature... Short version: I have managed to enable external control of the position of a Composition (and now can't easily disable it). 

At the beginning of this year I worked on a show where, without any tracking equipment available, I had to try and make projections follow a wall being flown up and down using Timeline animations. Since the cueing and motor-speed were variable, to say the least, I added a midi fader to allow me to adjust the position live, using a Formula (something like Tweenvalue + Midi_Fader_6) on the Y value. In some sequences, I would have liked to animate a Composition but, since the 'External Control' option isn't available, I had to add the position formula on each media item within the composition.

This month, the show is back and this time we have a linear tracker on the fly carrying the wall, which removes one headache. Because the director took the opportunity to add more media to the show, things have got complex enough that I decided to remove the tween formulas from sub-layers and drop my composition into a Virtual Display, which is then animated with a tween formula linked to the tracker, so that the tracking code is all in one place. The other day though, I wanted to check which Midi controls were still used in the show and, to my surprise, when I moved the midi fader, one of my Compositions also moved. This particular Composition had originally been a single media file, with a tween formula applied to it. When the director asked me to add extra layers to it, I created a new Composition with the original image cue plus the new layers, then dragged the Composition onto the existing cue to replace it. None of the media cues within the Composition have a any position tweens. On the Composition itself, the position tween no longer shows the green 'F' icon to allow editing of the tween formula and, of course, the 'External Control of Position Scale & Rotation' option isn't available in the specifications of the Composition, but it still responds to the formula added to the media cue which it replaced.

I guess the only way to disable the formula will be to work backwards - replace the Composition with an image file so that I have access to the 'External Control' option in the specifications, and can remove the position formula, then finally put the Composition back into place.

Having accidentally got this working, I could see that this 'feature' could be useful. It's much easier to add a single formula to one Composition cue than to all the source media cues. I almost hesitated in posting this in case this 'bug' gets removed in a future version! However, I assume there is a reason the option for external control doesn't exist - are there any drawbacks to having it enabled ?


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Hi Matthew,

Nice trick!

I've already tried to modify some options directly in the watch file to enable some unavailable features with more or less success, but your trick is way easier.

Regarding the composition position control from external input, to what I remember of the discussion I had with the dev team (a long time ago) the problem is there is no way to be sure all elements of the composition move in sync together, don’t remember if it’s on the same display or across several displays…

Now for your application it’s probably not a real problem.




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Salut Benoit,

As you say, in my case this only affects one Display output, so sync across multiple outputs isn't a problem, but I guess I will avoid using this 'trick' just in case.

Once I dragged an image file back onto the Composition, the Tween Formula icon immediately lit up green - so it was obviously still stored for the cue - and I was able to remove the formula and then restore the Composition media to the cue - so no more unexpected animation. 

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