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The limits of Twixtor

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Gavin bRIGGS
The limits of Twixtor
on Oct 21, 2008 at 12:54:22 pm

Hi,

I've been getting to grips with this fantastic plug-in and created some amazing slow motion video.

What I've noticed though, is that the best results always come from frames that don't have a lot of motion to being with.

If this is the case, I've been able to get results that look exactly like real slow motion video, even at 12.5% speed, or 7 inbetween frames.

When there's a lot of motion in the frames though, the quality of the output image breaks down. It no longer looks believable.

So I was wondering, is there a way, by setting up tracking points and creating mattes, to make any video sequence realistically slow? Or are there definite limits to what this effect can acheive?

I don't really want to waste a lot of time on video that won't look believable at the end of the day.

Thanks.


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Pierre Jasmin
Re: The limits of Twixtor
on Oct 21, 2008 at 2:53:24 pm



The most common limit in terms of an automatic process for this technology at large (not just us) comes from having part of a shot that goes one way and another region that goes the other way and under the other, which is not uncommon when you have camera motion combined with some action. It is a problem because at some point from a frame to another you end up with large occlusions -- areas of the image that are visible in a frame but not in the next one...

If you need a rule of thumb which is 90% of the time right, that would be if a pixel travels more then 5% of an image size on a frame then you are in potential trouble zone and that's when typically the "guidance" methods we offer such as: input of mattes separating "layers" of motion basically, and the input of point tracking data (for example will help large pans) and rotosplines (for example to disambiguate for Twixtor edges of a rotating object) become your friend if you are willing to spend the time doing it.


Pierre



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Gavin bRIGGS
Re: The limits of Twixtor
on Oct 24, 2008 at 9:24:06 am

I see, thanks. So if you're willing to learn all the functions and spend significant amounts of time on a clip, then there's nothing it can't slow down believably?

By believably, I mean when viewed on a large screen and still look like it was acually shot in slow motion.



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Pierre Jasmin
Re: The limits of Twixtor
on Oct 24, 2008 at 8:44:24 pm


For the most part yes.
One can always invent an image sequence which will fail, for example fast moving in all directions tiny black dots on a white background, ... or special problems like helicopter blades which have subsampling problem by definition at standard frame rates...

The worst I have seen in the near impossible category was a bunch of acrobatic extreme bicycle bunched together so you can see through the bicyle wheels other stuff moving. Trying to roto the inside of a bicyle wheel might be an unhuman task.

Pierre



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Gavin bRIGGS
Re: The limits of Twixtor
on Oct 27, 2008 at 3:41:59 pm

Cool, I'll keep plugging away with it then. Thanks for the help.



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