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Motion tracking and Plexus

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Stephen Brooks
Motion tracking and Plexus
on Nov 7, 2013 at 1:52:10 am


I wonder if you guys can help me. I'm a film maker, not really a motion graphics artist however I am always super keen to learn and have always been very interested in the capabilities of Plexus.

I am working on a piece involving a motorcycle onto which I would like to add Plexus. This requires motion tracking for the plexus points, the shots to be tracked are very simple, its a white motorcycle shot in a studio environment (against black) and I would like plexus to highlight certain sections of the bikes fairing/mudguards etc ... SO with that in mind I have the following in the way of motion tracking available to me : -

1. AE CC's 3D tracker .. It's brilliant however of course it decides the best motion track points and largely they aren't what I want. If I do apply plexus it of course works very well, right click on one of the track points, create null and Plexus2 adds a point ... excellent. Just not in the right place.

2. Mocha AE .. This seems to be excellent at tracking but I'm really not sure what I do with the transform data once I've copied it to the clipboard and pasted it to a null in AE. It doesn't seem to create an actual point, it sort of tracks an area, not a precise point on the bike. Even if I delete the anchor point on the tracking data and move the 'track' to where I want it when I try and add a light for example it just doesn't work (is this something to do with 2d/3d?)

As I say .. the plexus bit I'm ok .. I just cant seem to work out how I can tell Mocha/AE or whatever that I want to track 4 or 5 precise points on the motorcycles fairing, bring those points into AE as nulls or lights or whatever, apply Plexus and then work on the lines etc ...

I can attach screen shots if that may help ? .. do I need to host the shots off site?

Thank you for any advice !!!


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Roland R. Kahlenberg
Re: Motion tracking and Plexus
on Nov 7, 2013 at 4:04:05 am

On this video ->, I used AE's 2D Tracker and mochaPro for the different tracking tasks and of course Plexus2.

You can get 2D arrays (for position or effect points) to follow a 3D layer's position or a 3D layer's position or an effect's XYZ array to follow a 2D layer's position with the following scrip -

Track_MG = thisComp.layer("TrackPoint_Mudguard");

In your specific case, you will apply the Expression script to an aptly named (for easy management of your layers) 3D Null's position.
You will need four Nulls, one for each of the CP points.

The script for linking a 3D Null to a 2D layer's CP's Upper Right corner property, the script reads as such -

3DTrackPoint_UR.toComp([thisComp.layer("CP_Track_Mudguard").effect("Corner Pin")("Upper Right")[0],thisComp.layer("CP_Track_Mudguard").effect("Corner Pin")("Upper Right")[1],0])

You will now have to repeat and rinse for each of the other three points - three more 3D Nulls and remember to change the name for the appropriate CP corner property in the script, ie Upper Left etc.

Take note that mochaPro is able to export 3D Nulls after a successful camera solve. Unfortunately, mochaAE does not offer 3D camera solves.

If you want to export Transform tracking data from mocha, take note that the center of the Planar Surface is where the position property is when you paste the data into an AE layer.

Further, once you have a successful track in mocha, you can move the Planar Surface within the tracked plane to gather other position properties. You can of course do these offsets in AE using the Anchor Point. Another important thing to remember once you've exported Transform tracking data to E is to delete all the Anchor Point KFs and to reset the Anchor Point value.

Lastly, whether you can or should use AE"s built-on 3D tracker depends on your footage. If you do want to post a video then upload it to the COW and embed the URL in your post.


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

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Ross Shain
Re: Motion tracking and Plexus
on Nov 7, 2013 at 4:48:09 pm

If using mocha AE for this, I would recommend tracking with transform only as you probably want just x,y for the Plexus part. After you track, display the Surface (blue box) and scale and position it exactly to where you want. When exporting transform tracking data to AE, it will use the center of the Surface.

This should allow you paste the transform track from mocha AE to your Null and get something very accurate,

There is a tutorial that covers some of this, but I believe there are lots more ways to link Plexus to track data:

Hope this helps.

Ross Shain
Imagineer Systems

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Scott Green
Re: Motion tracking and Plexus
on Sep 5, 2014 at 10:41:02 am

Is it possible to use this technique for what I'm trying to achieve here?

I want to track some nulls (with graphics attached to those nulls) to specific points on my Plexus sea that I'm creating. The sea gets quite choppy towards the end and as indicated by my pink arrows it might be difficult to track the tiny points in the distance using the motion tracker as the point will overlap other point and get confusing, and in my head I don't think it will work.

I'm wondering if there's a way to pick the data from a particular point and link it to a null somehow or if you have any suggestions?

Music Videos, Motion Graphics, Creative Multimedia, Video Production, VFX and Graphic Design by Splurj Creative Multimedia

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