Rotoscoping, what am i doing wrong?

Hi Forum,

I am not completely newbie on kdenlive however, when I use the rotoscoping effect (masking) it gets really frustrating because it seems that the mask i create keeps on changing and contorting as the clip goes.

No problem if it is a straight line, door, or road but when it’s all twisted and I have to add many keyframes things get twisted.

I will try to explain it better.
I have a contorted path that I would like to mask and make an effect as if the highlighted route moves as the clip goes so, I choose a few initial keyframes, then I scroll forward (at the moment I am going 5 keyframes at times). It seems to do what I expect.
I scroll back a few tens keyframes and i adjust where necessary but then, for some weird reasons, the original mask has changed shape and there are more (lots more) keyframes to be added/changed.

It seems that the mask has some magnetic re-shaping every time I change or add a new keyframes in between the ones I have already placed. Let’s say I have a square mask with 8 keyframes, one every 5 flip-frames; i add on keyframe and the mask become a rhomboid and even if i delete the last added keyframe the shape of the mask remains all twisted.

It’s really frustrating because when I think i am finished, I add/change one or two keyframes and I have to start almost everything again.

I am trying to mask a clip of about a thousand keyframes and from the initial 150-200 rotoscopy points that I was calculating, I am ending up almost with a 900 rotoscopy-points (one-by-one)

Am i missing some settings to avoid the mask reshaping/changing every time I make adhustments?

What am I doing wrong?

Thanks in advance

Are you adding points to the rotoscoping shape when adding keyframes?

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I think I am (the true answer is YES but it seems that I can’t just answer YES!

Is that the problem?

It could be because even though Kdenlive keeps somewhat track of when a new point was added to the rotoscope shape, it may get confused still. For example: I started with a rectangle (4 points), moved forward a few frames and added a keyframe, then added a new, 5th point, skipped forward a few more frames and moved it. All good: New point appears at the right keyframe and moves to the new position. But then I went back to a frame where the shape still had 4 points and added a fifth. When moving along the frames, this newly added 5th point’s position became the starting position of the 5th point I had added before.

So, in your case you need to pay attention when you add what point to the shape, and which points you had added earlier in time but later in the timeline and the position when you added them and where they are moving.

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Thank you. That makes perfect sense.
I will try to pay attention to this small thing from now on.