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Twixtoring real bullet-time footage ?

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Julien Herman
Twixtoring real bullet-time footage ?
on Aug 29, 2013 at 3:18:57 pm

Hi everyone,

I need some help on an important project we're trying to achieve, here's the situation:

We've got fifty Canon G15 cameras put onto a circular ramp to make the famous "bullet time/timeslice/timefreeze" (whatever you call it) effect.

Since we encountered many issues synchronizing those cameras, we decided to make the sync while using a low shutter speed in a dark environment, and make the cameras shoot at the same time by using flashlight.

So I stabilized the shots, it works, but now I need to slow down the video using Twixtor.
As I want the footage to slow down dramatically, up to 20% would be great, I get some ghost images.
I tried to use tracking points but I guess my knowledge of the twixtor plugin reaches its limits.

1 - Is there any way to upload a sample video so you can see by yourself, and already tell me if it's possible or not ? and give some advice ?
2 - Is there any interesting resources on the internet on the subject? Tutorials made by professionals that cover entire plugin ? (and not just some parts like we use to see it on Youtube and stuff...)

Thanks for helping.
Best

Julien

http://www.julienherman.com


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Pierre Jasmin
Re: Twixtoring real bullet-time footage ?
on Aug 29, 2013 at 4:08:06 pm

Sure, hit the support menu and you will see a contact form on left side. This will send you a way to upload to our ftp zone OR simply drop it somewhere else and send a note to techsupport at revisionfx dot com.

I really need to see the camera layout and content to respond better.

Pierre



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Pierre Jasmin
Re: Twixtoring real bullet-time footage ?
on Aug 29, 2013 at 4:11:26 pm

Also, if you hit the help menu on top of the site it brings you to our tutorial site

We actually have a tutorial coming for multi-view interpolation coming - give us a couple of weeks

Pierre



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Julien Herman
Re: Twixtoring real bullet-time footage ?
on Aug 30, 2013 at 8:19:34 am

Hi Pierre,

thank you for helping.
I Couldn't find the support menu here on the cow, so I've simply uploaded the files:

http://www.filedropper.com/sample-videos_1

There are two files, one in Apple ProRes422 format, the other in H264.

For this test, we didnt use the whole fifty cameras but only 21. Besides, the background is very empty, but we may use more detailed background in the future as we want to show real life environment.

Here is an example of what we want our video to look like (considering the fact that we don't have as much cameras as they do):




Do you think, it is possible to achieve the same result ? (with less amplitude of course..)
Thanks again for helping

Julien

http://www.julienherman.com


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Pierre Jasmin
Re: Twixtoring real bullet-time footage ?
on Sep 3, 2013 at 3:41:41 am

Julian

1) the filedropper link does not work for me

2) I meant on our website - revisionfx.com



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Julien Herman
Re: Twixtoring real bullet-time footage ?
on Sep 3, 2013 at 8:09:29 am

Ok the link has been broken, here is another one:

https://mega.co.nz/#F!655EVTIK!SAOFJV6USbl-ZZnuHU09Cw

thank you.

Julien

http://www.julienherman.com


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Pierre Jasmin
Re: Twixtoring real bullet-time footage ?
on Sep 3, 2013 at 3:59:35 pm

The main issue is the big strip of paper in front of the people
Where the strip passes in front of the subject, the virtual camera is moving so fast, that it creates very large occlusions from frame to frame, i.e. on one frame you see the guy with the white shirt, on next you don't.

This would work a lot better if shot on separate layers over a green screen or something.
That said the theory is you would need to roto the strip (a matte) to pass as layer to Twixtor PRO and possibly animate some guiding roto-splines for Twixtor (spline support only available in AE and Fusion, used to work in Combustion and Shake but these applications are no longer supported).
When the white shirt guy appears and disappears frames you would still get some artefacts for these sections that might or not be acceptable.

If this was shot in two passes, where the strip is suspended by wires by itself on a pass (and you could possibly key it out) than the actors would be on their own pass and never hidden for such a large foreground area and it would work much better.

We have a few Twixtor PRO tutorials (+ doc, + a couple of related sample projects) on help.revisionfx.com

Pierre
pierre at revisionfx dot com



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Pierre Jasmin
Re: Twixtoring real bullet-time footage ?
on Sep 3, 2013 at 7:21:39 pm

Since it's not a lot of frames you can try this:

Create a pretty tight matte for the foreground layer from your paper strip
In Twixtor PRO this will be the foreground matte

I also added two splines, one for foreground on strip - you would need to animate this to follow (see doc)
And one for the background so the wall corner stays perfect -- note don't shrink the spline, just make it on widest view and move-animate the bottom point of line.





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Julien Herman
Re: Twixtoring real bullet-time footage ?
on Sep 4, 2013 at 8:29:19 am

Hi Pierre,

First, thank you very much for your time and help, much appreciated.

I will study those docs you're referring to.

We can't shoot on a green screen since we want to use a real environment.
If the big strip of paper is the main issue, we could simply consider not putting anything in front of the people for the next tests, though thank you for the "spline" techniques explained.

What I really need to be sure of, is mainly about the camera move, and if the amount of frames would be enough to get something close to the footage I gave earlier:



(making of, if it can helps...)

Since we don't have as many cameras as they do, do you think twixtoring the footage of 50 cameras would do the work ? What are the do's and don'ts in this kind of project ?

I know it is hard for you to answer without the material so we're going to do another test today with the fifty cameras, see what kind of issues I get this time...

Our goal is to manage to slow down our footage, on different projects, different sets, and get it as clean as possible in any cases.

Talk to you again soon.

Best

Julien

http://www.julienherman.com


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Pierre Jasmin
Re: Twixtoring real bullet-time footage ?
on Sep 4, 2013 at 11:03:09 pm

On your test seems the actors interpolate OK at that distance between cameras - the main issue is the large paper strip in front...

understood about green screen not being an option...
one thing that would probably work here instead of chroma key since the camera are essentially locked would be to shoot a set of images without anything so you can just difference key



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