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Motion Tracking with Moving camera vs. object

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Erik Boles
Motion Tracking with Moving camera vs. object
on Nov 20, 2009 at 9:00:39 am

If I have a video where the camera is stationary but the object in the video is moving, I can successfully track something to it (for example, pin an image to a bus moving down the road (in and out of frame)).

Here is the problem: I have a TV that is off in frame, the TV doesn't move, the camera moves away from the TV (so the TV goes out of frame). I am trying to pin a video to the TV, but when the TV goes out of frame, the video I tried to pin to it doesn't track with it, it stays right where I had it.

what am I doing wrong?

Erik
twitter.com/ErikBoles


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Mikey Bouchereau
Re: Motion Tracking with Moving camera vs. object
on Nov 20, 2009 at 3:17:16 pm

Is the video you are trying to pin to the camera a 3D object? It sounds like you are using motions camera to have the TV screen leave the frame. If the video is just 2D it will not be effected by Motion's Camera movements leaving your video where it was.

Mikey B!

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Stephen Smith
Re: Motion Tracking with Moving camera vs. object
on Nov 20, 2009 at 4:05:14 pm

Does the TV rotate as it moves or is it flat? Any way you can post the shot?





Stephen Smith
Utah Video Productions

Check out my Motion Training DVD

Check out my Motion Tutorials


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Erik Boles
Re: Motion Tracking with Moving camera vs. object
on Nov 20, 2009 at 7:41:17 pm

Stephen,

The TV is mounted to a wall and is stationary, it doesn't move. when I try and 'pin' the motion points to the TV, they do 'snap' to the TV.

Erik

http://twitter.com/ErikBoles


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Stephen Smith
Re: Motion Tracking with Moving camera vs. object
on Nov 20, 2009 at 7:55:03 pm

If I could see the clip I could give you a better description on how to do this. It sounds like you may not need to do a 4 corner pin. You may be able to get away with just doing a one or two point track. Just track the edge of the TV that stays in the scene the longest and you should be good to go. That being said about footage I've never seen. Hope this helps.




Stephen Smith
Utah Video Productions

Check out my Motion Training DVD

Check out my Motion Tutorials


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Erik Boles
Re: Motion Tracking with Moving camera vs. object
on Nov 21, 2009 at 2:47:19 am

Stephen,

I will upload a video tonight and reply to this post with a link. thanks tons for all of your help.

E


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Stephen Smith
Re: Motion Tracking with Moving camera vs. object
on Nov 21, 2009 at 3:10:10 am

Sounds good.




Stephen Smith
Utah Video Productions

Check out my Motion Training DVD

Check out my Motion Tutorials


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Erik Boles
Re: Motion Tracking with Moving camera vs. object
on Nov 20, 2009 at 7:36:03 pm

Mikey,

Thanks for the quick reply. i am not using the cameras in motion at all, the raw footage was the camera itself moving to another object in the room, away from the TV. when doing motion tracking (and pinning the movie to the television), should i have it set to 3D mode vs 2D mode? I didn't try it in 3D mode.
E

Erik

twitter.com/ErikBoles


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Jim Johnson
Re: Motion Tracking with Moving camera vs. object
on Nov 20, 2009 at 7:16:23 pm

Howdy,

This is the kind of situation where a good 3D track makes the shot a no-brainer, rather than a potentially-tweaky 2D four-corner pin. PFHoe, which is a "lite" version of Pixel Farm's 3D tracker, is cheap and can export 3D matchmove for Motion (as well as a bunch of other apps).

In PFHoe, you can just tag the position of the TV screen and it will give you a Motion project with a solved camera and a 3D group that is located at the 3D position of the TV screen. Then you just drop your replacement image into the group and you're pretty much good to go.



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Erik Boles
Re: Motion Tracking with Moving camera vs. object
on Nov 20, 2009 at 7:46:55 pm

Jim,

I appreciate the input, but this isn't something that complex, and I have seen it done in motion many times, so this is just something I am doing wrong, not something that is going to be solved by another $100 worth of software after spending $1,200 on FC Studio.

Erik


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Jim Johnson
Re: Motion Tracking with Moving camera vs. object
on Nov 20, 2009 at 9:32:19 pm

Howdy,

What you're asking to do has 3 solutions:

1. Hand animate the corner-points that move out of frame, because they can't be tracked when the feature (i.e. object being tracked) is no longer visible. This can work fine, depending on the length of the shot and how prominent (or not) the screen-replacement is.

2. Use the Offset Track option to select a new tracking feature for the point(s) going offscreen. This works best if the feature is moving perpendicular to the camera (i.e. 2D).

3. Use a 3D camera solver, then you can position objects wherever you want and they move or sit still properly.

If your shot is short and the camera move isn't too 3D (i.e. a lot of parallax shift), then you can use the Offset Track option. If the move is too 3D, then you can hand animate the offscreen trackpoints, but the quality will depend on how much elbow-grease you're willing to put in.

As for a 3D matchmover adding complexity...they've gotten so laughably cheap in the last few years that it's worthwhile to invest in them. It's functionality that neither the Studio nor any other product suite (i.e. Adobe) has built-in, so it's handy to have in your arsenal when it can save you a lot of time.



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Erik Boles
Re: Motion Tracking with Moving camera vs. object
on Nov 21, 2009 at 2:46:20 am

Jim,

Very helpful post, thank you so much for the input. I will play around with that a bit. I am also going to post a video to what I am doing to make sure I am not way off track.

Erik


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PJ Palomaki
Re: Motion Tracking with Moving camera vs. object
on Jan 18, 2010 at 3:34:02 pm

On PFHoe website it says that they export only XML file for Motion (not Motion-specific project/files), does this import into Motion without errors and glitches?


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Mark Spencer
Re: Motion Tracking with Moving camera vs. object
on Jan 18, 2010 at 3:47:59 pm

That's not correct on their site, it does export a Motion project - you can see an example here:

http://www.vimeo.com/7920607

(PFHoe to C4D to Motion)

--
Mark Spencer
Freelance Producer/Editor/Motion Graphics Artist
Apple-certified Master Trainer
Author, Motion 4 from Peachpit Press
http://www.applemotion.net


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PJ Palomaki
Re: Motion Tracking with Moving camera vs. object
on Jan 18, 2010 at 5:11:54 pm

Excellent!

Mark, do you know if you need the basicl PFhoe or the Pro to export direct to Motion?


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Mark Spencer
Re: Motion Tracking with Moving camera vs. object
on Jan 18, 2010 at 5:15:03 pm

I've only used the Pro version but I believe both will.

--
Mark Spencer
Freelance Producer/Editor/Motion Graphics Artist
Apple-certified Master Trainer
Author, Motion 4 from Peachpit Press
http://www.applemotion.net


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