Extrapolated null position based on two tracked points

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7 total messages Started by Navarro_Parker Fri, 13 Mar 2009 17:49

#347

Author: Navarro_Parker
Date: Fri, 13 Mar 2009 17:49

3 lines
944 bytes

The photo is pretty self-explanatory. If I have two tracked points, how can I determine the coordinates for a third position? I plan on wiring the distance of the extrapolated null to a slider to control the distance from the tracked points.

 <http://s175.photobucket.com/albums/w134/navstar/?action=view&current=extrap-null.jpg>

Re: Extrapolated null position based on two tracked points

#350

Author: Mylenium
Date: Mon, 16 Mar 2009 13:01

18 lines
1014 bytes

Determine the angle based on teh difference, then use it to drive sinus and cosinus:

Radius=thisLayer.effect("Slider")("Slider");

A=thislayer.Tracker("A").featureCenter;
B=thislayer.Tracker("B").featureCenter;

DiffX=B[0]-A[0];
DiffX=B[1]-A[1];

Ang=Math.atan2(DiffY,DiffX);

X=Math.cos(Ang)*Radius;
Y=Math.sin(Ang)*Radius;

[X,Y]

Mylenium

Re: Extrapolated null position based on two tracked points

#352

Author: Dan_Ebberts
Date: Mon, 16 Mar 2009 13:38

8 lines
962 bytes

You can simplify the math a little if you keep everything as vectors:

slider = effect("Slider Control")("Slider");
T1 = thisComp.layer("your_track_layer").motionTracker("Tracker 1")("Track Point 1").attachPoint;
T2 = thisComp.layer("your_track_layer").motionTracker("Tracker 1")("Track Point 2").attachPoint;
T1 + normalize(T1-T2)*slider

Dan

Re: Extrapolated null position based on two tracked points

#353

Author: Navarro_Parker
Date: Mon, 16 Mar 2009 19:37

1 lines
668 bytes

You guys are awesome! $$$ (or ���) for the tip jar! :)

Re: Extrapolated null position based on two tracked points

#354

Author: Navarro_Parker
Date: Tue, 17 Mar 2009 18:56

1 lines
722 bytes

That works great. Now how would I keep null rotation matched based on the vector formed by the two trackers?

Re: Extrapolated null position based on two tracked points

#355

Author: Mylenium
Date: Wed, 18 Mar 2009 07:20

3 lines
763 bytes

You simply use the angle my formula spits out --> radiansToDegrees(Ang). You may just need to add 180 degrees to reverse it...

Mylenium

Re: Extrapolated null position based on two tracked points

#359

Author: Navarro_Parker
Date: Tue, 24 Mar 2009 19:45

1 lines
636 bytes

Thanks -- I'll try it!

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