Re: 3rd Party Motion Tracker Plugin for AE? by Andrew Shanks on Mar 22, 2006 at 7:52:29 pm
Short answer is there is only one 3rd party tracking plugin I know of for After Effects (I played with the demo ages ago, but it didn't seem to be as accurate as the stock stadard version), ...but most of us that want more powerful tracking, look to matchmove software that works as a stand alone application, ...PFHoe and Syntheyes both export 2D tracking data in an after effects format as well as full 3D matchmove camera data in maya format that after effects can use.
The after effects tracker is okay when you get to know it, ...the key is to look for well defined high contrast areas in your image (corners are great), then do at least two tracks, ...one forward, then select the same feature again and do a second track in reverse, ...use an expression to average them, and there you go, you should have a less jittery, good track in most cases. :-) Other thing to remember is if you have a feature that goes off screen and you wish to continue the track on another feature, hold down Alt (or Opt on the Mac) and drag the feature box to the new target feature, ...the little crosshair feature target will remain heading in the direction it was going, so your path remains unbroken even though the feature is now wandering off onto the pasteboard off the side of the screen.
Goodluck!
Re: 3rd Party Motion Tracker Plugin for AE? by Eric Goldstein on Mar 22, 2006 at 8:04:31 pm
Andrew,
Thanks for the thoughts and tracking pointers. I have no trouble sticking with
a feature, but have had troubles with jitteryness (haven't tried averaging back
and forth tracks, but will) and with linking tracks when losing a tracking point
off screen (I didn't know that you could hold down option/alt to help connect
these points and generally end up doubling the frame rate to see both fields
and correcting with the anchor point. I'll give your suggestion a try).
I reffered back to the earlier tracking discussion and I'm going to demo some
of these products as well.
Thanks again,
Eric Goldstein
Giraffe Film Company
Los Angeles
eric@giraffefilm.com
Re: 3rd Party Motion Tracker Plugin for AE?/Averaging Expression by nicholastoth on Mar 22, 2006 at 8:59:08 pm
for its ease of use vs. price point, I'd strongly recommend just buying SYNTHEYE....
but this is coming from the cheapo who is trying to not use automatic duck and is losing his mind between AAFs and OMFs
Re: 3rd Party Motion Tracker Plugin for AE?/Averaging Expression by Colin Braley on Mar 22, 2006 at 11:58:19 pm
When I am averaging multiple tracks I use an expression like this:
//begin expression
tracks = [ ____ , ______, _____ ,_____ ,_____];
//don't modify below this line
p = [0,0];
for(i = 0; i < tracks.length; i++)
{
p[0] += tracks[i][0];
p[1] += tracks[i][1];
}
p/tracks.length
//end expression
All you need to do is highlight the spots that say ______ and pick whip to the attatch point property of a tracker. Add as many of these as you want just make sure it uses this format:
tracks = [pick whip to tracker one , pick whip to tracker two, pick whip to tracker three ];
On a little sidenote, you could use this script if you wanted to
http://www.aenhancers.com/viewtopic.php?t=136 I have never used it before, but it could be helpful if you do this kinda thing alot.
~Colin
Re: 3rd Party Motion Tracker Plugin for AE?/Averaging Expression by sebastien allain on Mar 23, 2006 at 7:19:59 am
I use a lot of expressions everyday that i make by myself. I've done an expression for such trouble too but not a so elegant one!
I do not use "+=" or "for(*,*,*)"... and i don't understand at all something like "tracks[i][1]"
Would you please take few minutes to explain to me how all your expression works ?
Thanks a lot
Re: 3rd Party Motion Tracker Plugin for AE?/Averaging Expression by Colin Braley on Mar 23, 2006 at 11:16:57 am
I'll try to explain the expression with some comments:
//begin expression
tracks = [ ____ , ______, _____ ,_____ ,_____];
//The line above makes an array of objects that can be referenced
//by using code such as tracks[0] which would be the first tracker
//tracks[2] would be the third tracker
//and tracks[tracks.length -1] would be the last tracker
p = [0,0];
//this line initializes a variable name "p" and makes it an array [0,0]
/*
This next line is where it gets a bit more confusing
I use something called a "for loop" to add up the x and y components of each of the trackers and put them in "p" (the variable i made earlier. for loops follow this syntax:
for( create a variable here; a condition for the loop to end; a condition to increment the variable that will be called at the end of the loop);
It is also good to note that any part of a for loop can be left blank.
Here is what is happening in my for looop:
-create a variable "i" and initiialize it to zero
-add to the x component of p the x componenet of the first tracker
-add to the y component of p the y component of the first tracker
-move on to the next tracker in the arrray "tracks"
Note that i used += (the add and increment operator)
a += b
is the same as saying:
a = a + b;
*/
for(i = 0; i < tracks.length; i++)
{
p[0] += tracks[i][0];
p[1] += tracks[i][1];
//I could have written this:
}
//In this last part I divide the x and y componenet of p by the number of trackers
//I could have written
// [p[0]/tracks.length, p[1]/tracks.length]
p/tracks.length
//end expression
I hope that helps you understand it better.
~Colin
Re: 3rd Party Motion Tracker Plugin for AE?/Averaging Expression by sebastien allain on Mar 23, 2006 at 11:42:55 am
Yeah !
My last question for today:
I have never seen the "for loop" syntax in the adobe'help doc. Where can i learn such syntax and condition form ?
Is there anything else but the "Scripting Guide AE.pdf"
Re: 3rd Party Motion Tracker Plugin for AE?/Averaging Expression by Colin Braley on Mar 23, 2006 at 3:34:05 pm
There are a couple types of loops in programming such as for loops, while loops, and do-while loops (I don't know if you can do these in AE). They don't cover this kind of stuff in the help docs, I learned it from a programming class (AP Computer Science AB) that I'm taking right now in Java. I would reccomend buying a book o Javascript and skipping over all the web related stuff and learning syntax of things like loops, variables, functions etc. I think on motionscript.com Dan reccomends a few books.
Re: 3rd Party Motion Tracker Plugin for AE?/Averaging Expression by Eric Goldstein on Mar 23, 2006 at 4:09:41 pm
Colin,
Thank you for taking time to explain your program.
The syntax is very like VBA, Microsoft's programming language that runs with Excel, Word, etc. There are a lot of beginning programming books for VBA and other basic languages that go over these concepts. I found the ones I have on Amazon.com.
Eric
By the way, if there's anyone out there like me who didn't know about holding down option/alt to connect segments
of tracks, it's great and has saved me a great deal of time. Averaging as described by Andrew and Colin has smoothed the
tracks greatly. I've also used field tracking, which has helped with smoothing things out. The script Colin refers to at the bottom of his initial post works great; just download it and put it in the scripts folder in AE. I looked through some of the third party tracking products suggest. SynthEyes seems to give the most bang for the buck ($399), and I think I'm going to purchase it. However, it was not initiallly able to get hold of any tracking points on the clip I was working on. It may be that I can manually assign tracking points, but I haven't had time to look at that yet. Otherwise, it has some impressive features.
Eric Goldstein
Giraffe Film Company
Los Angeles
eric@giraffefilm.com
Re: 3rd Party Motion Tracker Plugin for AE?/Averaging Expression by Andrew Shanks on Mar 23, 2006 at 6:55:40 pm
Hi Eric,
glad to see this thread has taken some good interesting turns in regards to the averaging of track points. In regards to Syntheyes, often the best way is to do a manual track on a couple of points (as in, do a track like you would in any 2d tracking application, ...correcting it when it goes astray, etc), then run the auto tracker afterwards, ...by doing the manual track first you give the software a guide as to the general movement within the shot, the auto process then uses this as a start point (like rough motion vectors to look for other points doing similar things) and should be able to lock onto a few more points. Sometimes footage just might not have much in the way of defined features (like a washed out, soft, or motion blurred scene), in these cases you may have to manually set track points (all matchmove/tracking software will have issues in such circumstances). The other thing i should point out at this point is that in order to do a proper 3D matchmove, you must have parallax in your image, ...i.e. your camera must be moving. If it is on a tripod you'll get little parallax with a pan(and if nodal, you'll get none at all), Syntheyes will give you a 2.5D solution if this is the case (tell it your camera is tripod mounted and it will lock its camera and try to work out pan and tilt info). Syntheyes is a big program that takes a bit to get your head around to use it effectively, but using it to track and animate the after effects 3D camera in order to track elements into scenes has helped me a lot in the past (plus being able to share the data with 3D colleagues in order to provide elements for my comps is great). Goodluck and let me know if you have any further questions.
