ADOBE AFTER EFFECTS: Forum Expressions Tutorials Creative Cloud

After Effects Mocha Tracking Issues

COW Forums : Adobe After Effects

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
Tyler Stegall
After Effects Mocha Tracking Issues
on Nov 13, 2013 at 7:04:32 pm

Hello, I'm trying to get my self familiar with Mocha AE CC for a project I'm about to start soon and I'm trying to do some basic tracking to get myself started.

As you can see I'm trying to track this simple rectangle I drew, but for some reason the track slips, sometimes badly no matter what I do.

Any tips?

http://i.imgur.com/yB8EBLi.jpg?1

Here is a picture for reference.

ALSO!!!

In my actual project I will be taking footage of Chess Pieces on a chess board. I want to be able to use Mocha Pro to map out the 3D data of the angle/perspective the chessboard sits in space. I want to be able to highlight different squares on the chessboard, so I can add in some 3D, or just change effects on the square in after effects. Could someone give me an idea on how to go about doing something like that?


Return to posts index

Roland R. Kahlenberg
Re: After Effects Mocha Tracking Issues
on Nov 13, 2013 at 8:43:56 pm

Based on the screen grab you posted, here are my observations -
1) Min % of Pixels Used is extremely small. It's best to set this to 90% and even higher for trickier tracks.

2) Your tracking splines cover an area with a sheen. It's not difficult for me to imagine that the sheen will not be static when the camera moves. The movement of the sheen will very likely be different from the movement of the surface/area that you are tracking. Hence, it should be expected that your tracking results will fail miserably.

3) Optional tracking areas includes just the outline of the lined square. Your tracking spline can (and possibly should) include the area just outside of the line. The high contrast between the line and its adjacent pixels will provide the tracking algorithm with a better tracking target.

You may want to add tracking splines to the edges of the surface. For tricky tracks, adding more tracking splines on co-planar regions helps the tracker by giving it more information to work with. More good information leads to better tracking results.

4) With respect to your expected project, it's hard to say if what you want to do will work without any issues. I expect there to be lots of occlusion as the different pieces will occlude each other with camera movement. The other problem areas include - a set of chess pieces will have very similar color/texture under natural lighting and the lack of contrast may hinder good tracking results.

HTH
RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects CS6 ACE/ACI


Return to posts index

Tyler Stegall
Re: After Effects Mocha Tracking Issues
on Nov 13, 2013 at 9:21:46 pm
Last Edited By Tyler Stegall on Nov 13, 2013 at 10:00:13 pm

Thanks for the reply your response was very helpful.

There were a few things I did not understand however. What do you refer to when you say optional tracking areas? When you say adding more splines and co-planar regions, I know how to add more xspline points, but what are co planar regions and how can I add them.

In the end I'm going to want to be able to track the board's squares and place a shape on some of them and make it look like its sitting on the board just like a chess piece. The chess board will be mostly empty with no more than 2 pieces on the board at any time.

Also, for some reason when I turn on the grid feature, it never seems to be on the same plane or perspective as the plane I have it on


Return to posts index


Roland R. Kahlenberg
Re: After Effects Mocha Tracking Issues
on Nov 13, 2013 at 10:11:22 pm

[Tyler Stegall] "What do you refer to when you say optional tracking areas?"

I should have said "additional" tracking areas as it would be clearer. You can add multiple tracking splines onto a single layer in mocha. You add these additional splines with the Add Spline tool.

[Tyler Stegall] "what are co planar regions and how can I add them"

A coplanar region is an area that shares the same planar surface as your main tracking area/region/target. In the screen grab you provided, the edge of the tracking surface is coplanar to the lined-square. So, draw a tracking spline to encompass the edges but ensure that you do not encroach too much into adjacent planar surfaces as these areas would be non-coplanar to your tracking target.

I would also like to suggest that you experiment tracking this footage without Perspective and Shear in the Motion section. Unless, your tracking are displays highly perceptible perspective/shear changes, it is best that you do not switch these on. The tracking algorithm tracks on a frame-by-frame basis. On such a basis, frame-by-frame, the change in perspective may not be picked up by the tracking algorithm. However, the change in transformation will be picked up by the tracker.

Two to three pieces is a good idea. Once you've taken out the issue of an animated sheen on the surface of the board, you should be fine. PLUS there is no harm in shooting a test footage for you to practice with. The edge of the board may also be an ideal target for tracking.

HTH
RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor
& Adobe After Effects CS6 ACE/ACI


Return to posts index

Tyler Stegall
Re: After Effects Mocha Tracking Issues
on Nov 16, 2013 at 8:56:36 pm

Here is an example of some of the issues I am having. I have every tack on the same layer, but for some reason the track keeps slipping as the camera begins to pan up.

http://i.imgur.com/sWyA1YB.jpg?1

This is a little frustrating because I want to be able to use the camera solve feature to add some cool layered 3D effects out of Cinema 4D.

Any advice on why this is slipping, or how to make it stop?


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]