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Motion tracking/time mapping for a ski video???

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scott donald
Motion tracking/time mapping for a ski video???
on Feb 19, 2011 at 9:08:34 pm

I recently bought a GoPro so going to be dabbling in making my own videos and edits...

i came across this video -







and at 1.21 into the video there is a jump and during the jump there are freezes and the skier stays there but the video continues and this occurs a few times during the jump before he lands...

as far as my understanding goes it must use time mapping and motion tracking but i have tried and failed now after a few hours to get this to work at all!!!

hows is this done??? does anyone know of a tutorial???


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Dave LaRonde
Re: Motion tracking/time mapping for a ski video???
on Feb 19, 2011 at 11:18:56 pm

Before we answer, we need to know something: how well do you know After Effects?

Do you measure your experience using it in years, months, weeks, days or hours? It makes a difference.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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scott donald
Re: Motion tracking/time mapping for a ski video???
on Feb 19, 2011 at 11:55:59 pm

i ould say my overall experience being high - computing degree so using final cut and other programs but for after effects i would say 3 months of use understand the program as a whole and followed many tutorials... but this has completely stuck me and its frustrating as i am normally good at working these things out...


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Joey Foreman
Re: Motion tracking/time mapping for a ski video???
on Feb 20, 2011 at 11:00:23 am

It doesn't look like time-remapping to my eye. But motion-tracking, yes. I think a Luma Key or a high-contrast luma track matte was used to extract the skier from the sky, and the extracted stills from several postions lain over the original footage, attached to the track points.

Use Mocha to generate the track.

Joey Foreman
Editor/Compositor/VFX Artist


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Angie Taylor
Re: Motion tracking/time mapping for a ski video???
on Feb 20, 2011 at 11:44:48 am

Hi there,

you can also achieve this effect with a combination of Motion Stabilization and the Echo filter (or perhaps Time Blend?). See another example here;







The first step is to Stabilize the footage. Then nest the comp into a new comp and apply the Echo filter, this will create an echo trail of anything that's moving in the footage. (This is why stabilization is important before applying it)

You will need to set the time intervals at a longer duration, perhaps -10 frames? And the instances should be set at how many 'copies' you want to create.

Once you have it as you want it you can then nest this in another comp and add reverse stabilization if you want the hand held look re-introduced.

Hope this helps!

cheers,

Angie

Angie Taylor animation & illustration for television, film, web and devices

http://www.angietaylor.co.uk
Twitter: theangietaylor
Linkedin: theangietaylor
http://www.facebook.com/pages/Angie-Taylor/118378194869002



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scott donald
Re: Motion tracking/time mapping for a ski video???
on Feb 20, 2011 at 10:20:46 pm

thank you for the reply... i can see how that will certainly work but i am having a nightmare in stablizing the video...

i am using this tutorial for stablizing...

http://library.creativecow.net/articles/swanson_grant/Final2_mixdown2/video...

but as far as i can tell the video is stable using the keyframe method... tried different tracking points and tried a numerous times...

but when i apply the echo it just screws up the colours, sort of luminous effect and does nothing...


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Joey Foreman
Re: Motion tracking/time mapping for a ski video???
on Feb 21, 2011 at 11:09:36 am

Do you have CS4 or CS5? If so then you should really use Mocha, which comes bundled with those. It's an astonishingly better tracker than AE's, tracking whole planes rather than single points.

And i don't think the effect in the video was achieved with the Echo effect. If you want clean, multiple instances of the subject then it must be isolated from the background. In most cases this will require Rotoscoping. But in your example video, the subject was shot against a bright sky which makes for an easy Luma Matte. If you have CS5, you can also try the Rotobrush tool.

The motion track will give you a sequence of Attach Points for a series of extracted stills or Freeze Frames of the subject. These are then laid out along the timeline over the original footage, staggered in time. You can then fade their opacity in and out individually.

Joey Foreman
Editor/Compositor/VFX Artist


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Angie Taylor
Re: Motion tracking/time mapping for a ski video???
on Feb 21, 2011 at 11:28:23 am

I agree with Joey that Mocha AE is best for the stabilizing. Check it out, as he says, it's much better than AE's default stabilizer.

But I'm afraid I have to disagree with Joey about the Echo filter - sorry Joey! I've done this technique a million times using the Echo filter, it's perfect for this and it definitely works, no need for rotoscoping if the footage is stable. We used to use this in lots of music videos in the 1990's, it was way over-used at that time and I was asked to create the effect on nearly every job I did for a while. I wouldn't recommend it as a solution if I didn't know for sure it could be done. Check out Youtube too for lots of examples of this technique using the Echo filter. Actually, you know what, I'll post a tutorial for it on my blog this week too, watch this space! :-)

The problem that you're experiencing in regard to the image looking like the 'luminance' is affected is due to the default settings of the Echo filter and the fact the image is not yet stable. You need the background to be absolutely stable before applying it. And what I forgot to add in my initial response is that you also need to change the 'Echo Operator' to either 'Composite in Front' or 'Blend'(depending on the look you want). The default is to use an 'Add' operator which will composite moving elements using the Add blending mode which will tend to brighten the luminance as you have noticed.

Hope this helps!

cheers,

Angie

Angie Taylor animation & illustration for television, film, web and devices

http://www.angietaylor.co.uk
Twitter: theangietaylor
Linkedin: theangietaylor
http://www.facebook.com/pages/Angie-Taylor/118378194869002



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Joey Foreman
Re: Motion tracking/time mapping for a ski video???
on Feb 21, 2011 at 12:03:25 pm

Sorry, I overstated the case if I implied that it couldn't be done with the Echo Filter. I just didn't think it looked like it was used in the example the OP posted. The repeated instances appear to be stills or freeze frames.
Also when I said "attach points" I meant Position Keyframes.
As usual in AE, there are lots of ways to accomplish the same effect.

Joey Foreman
Editor/Compositor/VFX Artist


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Angie Taylor
Re: Motion tracking/time mapping for a ski video???
on Feb 21, 2011 at 2:54:47 pm

Hi Joey,

I'm sorry too if I misunderstood. You're absolutely right, there's definitely more than one way to skin a cat in AE! That's what I love about it, everyone finds their own way of using it. :-)

Actually, you pointed out an important point, the instances are still, as opposed to moving frames. It could have been CC Time Blend FX that was the culprit in this case! Time Blend FX allows copying and pasting of frames to new times. A very neat but under-used plug-in. :-)

cheers,

Angie

Angie Taylor animation & illustration for television, film, web and devices

http://www.angietaylor.co.uk
Twitter: theangietaylor
Linkedin: theangietaylor
http://www.facebook.com/pages/Angie-Taylor/118378194869002



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scott donald
Re: Motion tracking/time mapping for a ski video???
on Feb 21, 2011 at 12:26:16 pm

thanks guys... really appreciating the help here... and its certainly making me learn fast and really enjoying it.

Well never used mocha and yes i do have CS5 so exploring it right now but will have more time later on today. going through the pdf manual. But certainly the tracking looks far better form m 20minutes on it there...

Would it be cheeky for you to use one of my videos for the tutorial Angie???


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