Problem Motion Tracking

[drummerboy678]

Hey guys,
Relatively new to After Effects, but I know enough to get myself out of trouble in most cases... Can't figure this one out though. I'm using AE's Motion Tracker to track a shot so I add an element layered on top.

I've gone through creating a track-point and analyzing the data. I click "apply", which according to this tutorial:
http://www.creativecow.net/articles/kramer_andrew/sky_replacement/sky.html

will add your tracking data to the clip above your tracked footage, however it doesn't. Although my track points stay on the right pixels, the clip above doesn't move, and there are no keyframes added to its "position."

Anyone experienced trackers understand this or have any solutions? I can post some screenshots if necessary.

Thanks in advance,
Taylor

[Matt Grunau]

You have to make sure that you are applying the track data to the layer you intend. If you click "Edit Target", in the Motion Tracker window you have a popup that allows you to pick which layer you want to apply the track data to.

Here's a good tip though, DON'T apply it directly to the layer you want to be tracked. Sounds strange, but what works best is to quickly create a solid layer (any color) and apply the track data to that. Then hide that layer, and parent the layer you want to be tracked to the solid. Why go through the hassle of an extra layer? Well, usually when you apply track data directly to the layer you want, the position will immdeiately be thrown off. So if you had say a sky replacement layer, perfectly lined up and you you apply the track data to it, its position gets thrown off. Then you have to go back and adjust the anchor point to get it back to where you want it. If you simply parent it to your solid, it stays in place and moves exactly as if the track data was applied to it. Also, you may wish to incorporate more than one element as part of your replacement. Maybe you have a nice plane, helicopter, UFO, midget, etc you want to add. Instead of reapplying the track data to each new element and then going back and lining them up where you originally wanted them, you simply parent them to the solid layer.

Huge time saver.


You could also use a null object, the effect is the same.

[Andrew Brinkhaus]

Most prefer Null Objects because they do not contain anything visually distracting, even though you can just turn a layer visibility off if it does, but basically yeah exactly what Matt said!

[drummerboy678]

Thanks for the advice... I found that "edit target" button, which was where my problem was. I've done a lot of motion tracking in MAYA, and was assuming AE would be pretty similar, but I'm having some trouble.

The basic effect is a pan around the table, showing 3 poker players all looking at their hands. As they peer up the cards, I want the actual suit/number to be visible through the card (its from the POV of a player who is real good at "reading" people's hands).


http://img252.imageshack.us/img252/9687/84812036hk3.jpg (http://imageshack.us)

http://img402.imageshack.us/img402/783/56418703uo7.jpg (http://imageshack.us)

http://img404.imageshack.us/img404/8166/36351362bv0.jpg (http://imageshack.us)

http://img404.imageshack.us/img404/782/13518226zy2.jpg (http://imageshack.us)

http://img122.imageshack.us/img122/1852/kdcopyrg0.jpg (http://imageshack.us)

Where would be the best place to track? I attached a few stills to show what I'm trying to do. I know I'll have to put a warp on the cards when they bend (and change the blending modes), but I dont know whether to track the chips (which dont move), or track the cards (which are peered up).

I appreciate any help, thanks for the advice already.
Taylor

[Matt Grunau]

Is the person going to see through the cards (like xray vision, but not the look of xray, only in concept) while they are away from him? And I take it the POV is the camera?

The bending of the cards you will have to do in your 3D app with bending a poly that is textured, or you could afford yourself a little cheat and only reveal the card after the it has been bent and seen by its holder and avoid the animation and 3D.

If there are three separate players, motion track three separate passes, one for each player's hand. Then composite accordingly.

One track won't be enough, and in fact would be more of a hinderance. Especially with rotating camera, where the cards will go out of shot. So track each hand, simply picking a place in the timeline you wish to start and a point to end, per "card exposure". Then apply each track data to a separate null (for each hand), bring in your texture or 3D animation, and put it together.

[drummerboy678]

matt... thanks for the advice and the fast reply. i'm going out of town, should be getting back to work on this in about a week... i appreciate the help, i may post another problem if I run into one.

[Matt Grunau]

Null persp, chummer.

That's what I am here for. Lets see a result when you have something though, to see if what I suggest is valid, or will end up looking like crap. :beer: :beer: