Motion Tracking with Moving camera vs. object

[Mikey Bouchereau]

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]

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

Utah Video Productions

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[Doyle Rockwell]

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.

[Erik Boles]

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

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[Erik Boles]

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

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[Erik Boles]

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

[Stephen Smith]

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.

Utah Video Productions

Check out my Motion Training DVD

Check out my Motion Tutorials

[Doyle Rockwell]

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.

[Erik Boles]

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

[Erik Boles]

Stephen,

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

E