Tracking 3d Body To 2d Body, Need Help

[mindspan]

Can anyone offer any sage advice, tips or ideas on a workflow for tracking 3d character geometry onto the 2d plates of the actors so that it matches their movements? I think i am close to having a brain hemorrhage. I know they do this in feature films all the time without motion capture but it seems so impossibly difficult. Any ideas?

[gmask]

Well are using a 3d tracking program?

On some occasions I can get away with just eyeballing it Maya.. it's relatively when it's any object that only moves up and down.. in which case you might consider usign a 2D tracker like the one in After Effects or Combustion or whatever.

If you really complex tracking then you might check out Syntheyes because it's very powerful and cheap at $500 in comparison to programs like Boujou which costs thousands.

[mindspan]

it almost seems like it would have to be done by hand, because you have to nail the animation of the digital double to match the actor while simultaneously tracking it. do you think an off the shelf package would help with that?

[gmask]

One possiblity is to stabilize the image based on the part of the body you are replacing and then animate by eye over that. It's hard for me to give specific advice without seeing the plate or getting a description of the action

There's a mel script that let's you zoom into the view for this sort of thing.. can't think of it off the top of my head.

[mckarp]

I've done lots of these on big feature films and there is quite a bit to know.

You should check out Tim Dobbert's matchmove book and also his Gnomon DVD on Object Tracking,
http://www.amazon.com/Matchmoving-Invisibl...2100&sr=8-1
http://www.thegnomonworkshop.com/dvds/tdo02.html

Some of the studios have special tools that allow a 2D track to drive the motion part of the IK chain, etc.

But the reality is that most character "matchamation" is primarily hand tracked. It is one of the more difficult and Zen like aspects of matchmove.

You must identify why you need to matchmove of the character. If you want to generate a CG shadow from a blue xcreen actor, then you focus on matching the feet, e.g.

Entire chapters of books are written on character matchmove, but here is a starting point:

Find a good frame where the 2D image of the character is "neutral". Start line up at that frame.

IK biped characters generally animate from the hips. Line up the CG hips so that the pelvis points the same way. You may want to attach rods to the hips that point out to the x and z axis.

Make sure that when you bend the knees properly, that the height of the character is still correct. If not, you'll need to move the character closer or farther away in screen Z space. Or, the limb length will need to be changed in the rigging.

Be sure to watch the matchamation from an "inspection camera" (not the render camera) looking at your character from the side, off axis from the render camera. It is common for the animation to look smooth from the front, but to be very jerky in screen Z camera space.

You may e-mail me with questions, but unfortunately, the easiest way to learn this is to work with a supervisor who has done it before. That's how I learned. Did lots of animated character matchmove on X-Men2, ScoobyDoo2, Garfield, etc.

Again, check out the Dobbert book/DVD

[mindspan]

I ordered the dvd and book that you recommended. I live in the central US and do not know anyone else in the effects field so I usually find myself havving to figure things out on my own. I cant thank you enough for giving me a starting point!