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Strange behaviour of planar transform node

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Erwin Bresslau

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Strange behaviour of planar transform node

PostTue May 19, 2020 11:06 am

Hi guys,

very sorry for the long post but I could´t figure out how to decribe the problem shorter...

Following one of Gerrit Hardings great YT tutorials, this one on creating a “demon eye effect” I came across a seemingly very strange behaviour of the planar transform node (I´m using DVR 16.2). What you do for the effect basically is you create a black background, attach a spline node to the background node and mask the form of the (real) eye, so you get a black demon eye which is supposed to go over the original eye. Then you track the movement of the real eye with a planar tracking node, from that you create a planar transform node (take the planar tracker out), connect the output of the background node (with the demon eye) to the planar transform node and feed the output of the planar transform node to a merge node between the in and out node.

The tracking of the eye works fine, the tracking polygon nicely follows the real eye which I want to cover with the “demon eye”.

But, if I play the clip, the “demon eye” will remain stationary in it´s initial position and will not follow the head /eye in the original clip, but – hard to describe in words – it seems that there is some invisible mask (obviously shaped like a square) that will follow the (real) eye thus cutting of the “demon eye” as it passes over it (“total eclipse of the eye”). E.g. if the head moves to the left, it seems as if the demons eye (sitting still) is cut off on the right side by a vertical straight line which follows the head movement (same with movements up and down, so obviously whatever is cutting the demon eye off is square shaped). This behaviour is independent from form and size of the tracking polygon.

I tried various clips with the same result (clean project, just that one clip, otherwise untouched). I tried it on a different PC with DVR 15, same result. Then all of a sudden I found a clip that worked. I created a project where in one timeline I now have three clips which don´t work and one that works with identical setups (so it seems that this is one of the rare occasions where it´s somewhat likely that it´s not me being too stupid to follow procedures from a tutorial). Trying to find the difference it turns out that funnily it´s the size of the demon eye. The head in the one clip that works is bigger so that the “demon eye” is larger accordingly. And sure enough: If I go to the not working clips and just enlarge the size of the mask on the background node i.e. increase the size of the “demon eye” (I used ellipse node instead of the spline node to make testing simpler) once I reach a certain size, the clip works perfectly (I went to a frame where the demon eye was half cut off and increased it´s size in the ellipse node, suddenly it goes “plop”, the demon eye pops in the right position, now fully visible and will follow the real eye perfectly).

Gerrit has written me that he had the same issue creating the video and could fix it by softening the mask for the demons eye a tiny bit more, I couldn´t reproduce that one though…(maybe softening pushed the size of his demon eye over the critical threshold).

As a fix, I tried to decrease the resolution of the background (thus making the demon eye larger in relation to the background) but as soon as I dial in a resolution for the background node that deviates from the main clip the tracking doesn´t work anymore (although I have redone the tracking and creating of the transfer node).

I have searched the internet and this forum for a similar problem but could not find anything. If any of you guys would have an idea on how to fix this I would be most grateful!!!
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Sander de Regt

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Re: Strange behaviour of planar transform node

PostTue May 19, 2020 1:14 pm

That's a very long first post, that's unfortunately a bit short on actual information.
Usually in a situation like this it's a matter of nodes that aren't connected correctly to each other.
So we need to know a little more about your actual set-up.
In the past you couldn't attach images until you reached a certain post count, but I'm not sure if this limitation still applies.
Sander de Regt

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xunile

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Re: Strange behaviour of planar transform node

PostTue May 19, 2020 3:34 pm

I tried to recreate your scenario and had the same thing happen. With a small mask the problem you described happens. If I make a slightly larger mask, it works as expected. I'm not sure what is going on, I will try and figure it out but someone else might know what is going on.
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xunile

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Re: Strange behaviour of planar transform node

PostTue May 19, 2020 3:57 pm

I think I have found an easy fix, if you merge your Background node with another Background node connected to the Background input of the Merge node, and set it to transparent, you can use a small mask without the problem.
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Win 10 Home | Intel i7 - 10700f 64 GB 1 TB GB SSD 2 TB SSD
RTX-3060 12 GB | Resolve Studio 18.6.6| Fusion Studio 18.6.6

Win 10 Home | Intel Core I7-7700HQ 32 GB 1 TB NVME SSD 1 TB SATA SSD
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Erwin Bresslau

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Re: Strange behaviour of planar transform node

PostThu May 28, 2020 8:41 pm

Thank you so much, Eric!!! Your solution works just fine. You must have exceptional technical intuition, I wouldn´t have guessed that workaround in a Million years...)

It´s just great that you took the time not only to read through my long post but to experiment and solve the problem. Your help is much appreciated.

Wish I could mail you a beer...
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xunile

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Re: Strange behaviour of planar transform node

PostFri May 29, 2020 12:21 am

Thanks and you're welcome. I just have a couple years of using and trying different things in Fusion. I like trying to figure out problems both for the person asking and for myself.
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