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Motion Tracker and World orientation (floor plane)
Posted: 17 April 2019 12:43 PM   [ Ignore ]  
Total Posts:  25
Joined  2013-06-21

I have a job coming up that will likely involve the Motion Tracker.

So I have been picking up experience in it.  I am able to get good tracks now and understand (more or less) the tags and so forth.

One thing that bothers me is that I wish I had more control over the orientation of the world.

Often I can get a pretty good approximation but never perfect.  I notice the same thing in virtually every tutorial (including those here). For instance, the floor plane is often close to right but just slightly turned one way or the other. So placed items need to be turned into correct place.

Is there a tool that would allow me to more precisely orient the world (without messing up the track’s relation to the camera)?

Many thanks!

Lance

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Posted: 17 April 2019 02:35 PM   [ Ignore ]   [ # 1 ]  
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Hi Lance,

Please note that the tracking features are all based on pixelated reality, there will always be an error per tracker. The whole system delivers the precision not based on a single or a few trackers, hence the colorization from green (best to lilac (bad). Even if the tracker points during the 2D tracking move around, the 3D solve gives them one position, no wiggling around anymore. The colors will be less informative after the 3D solve, but yes, the green ones are more likely to be closer to the tracking pattern.

The question is, what makes one sure that a scene is off when the scene has no option to even manually track with vast care the needed patterns for a Plane or Vector definition? Since I have no scene-file from you, I have to assume all the possibilities. But, yes, exchanging footage is often presented with obstacles.

The best way is, of course, to have a manual track on those elements you know that they follow P.Y or any vector that is stable and verified. If that is not possible and even a large group of, e.g.,  Ground aligned trackers will give you not the orientation you need, with some caution you can do it manually.

One way is, without using any of the Tags (Vector or Plane) to place the Motion Tracker Object under a Null Object. Currently, something is going on with the Motion Tracker and being not able to be moved/rotated by itself (as it was possible in previous versions. I haven’t gotten any reply to my report so far.) The new Parent Null allows to adjust the whole system, it moves the camera as well the Tracker Nulls. But then any Tag that would orient things newly and more importantly it would scale the system, as it will change the orientation, as no tracker were available, to begin with.

My suggestion, until the locked state, is fixed (if it is an unwanted behavior), continue as before, set your tags for Plane and Vector. Then place an object in the scene that aligns with the orientation you presume to be right.
While this new object (outside the Motion Tracker) is active, set the Axis of the Working plane, then lock the Working plane.

https://help.maxon.net/us/#51893
https://help.maxon.net/us/#51902

However, at the moment there is some news on my report why the system is locked, I will update the few threads so far about it.

What I haven’t found mentioned anywhere, but what becomes clear instantly, is the fact that the Lens-profile needs to be done with the focal distance used during filming. A reason for that is the more and more use of still photography lenses in moviemaking. Those lenses have the tendency to breathe, i.e., to zoom lightly while the focus is pulled. This will not happen with full cinema lenses (Master primes for example), breathing is minimized there towards zero.
Typically the lens grid is closer, so one has to use a high f-stop (F/16; F/22) to get at least a clear reading, while the focus is set to something further.
Without proper Lens-profile, the whole tracking is questionable.

One tip: proper tracking is based on close-by points, the further away from the tracking feature, the less useable they are. Shoot UHD at least, and if possible, consider to apply motion blur later.

Here is a little clip, showing the Work-plane being adjusted to the orientation needed. Until it is communicated why the Motion tracker is currently locked off, this would be my way to do it.
https://www.amazon.com/clouddrive/share/3zA1HfYSLbBEd43CxgntCq4iFzSOGMhsdU5RlJTKJNO

All the best

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
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Posted: 18 April 2019 10:01 AM   [ Ignore ]   [ # 2 ]  
Total Posts:  25
Joined  2013-06-21

Thank you, sir for your kind reply!

Yes, I will explore that more. 

I ended up getting SynthEyes and am going to learn that software as well.

Best,

Lance

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Posted: 18 April 2019 10:14 AM   [ Ignore ]   [ # 3 ]  
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You’re very welcome, Lance.

It is never a bad idea to have Syntheyes as well. The amount of functionality it has and the vivid support over the years is certainly worth the money. It has even a script to export for Cinema 4D.
So, enjoy learning, and if you like to dive deep quickly, it is not a bad idea to have Tim Dobbert’s book (second edition) as well. It is a little bit dated…, but anything he writes there will undoubtedly save you a lot of time later on.

ENJOY

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Dr. Sassi V. Sassmannshausen Ph.D.
Cinema 4D Mentor since 2004
Maxon Master Trainer, VES, DCS

Photography For C4D Artists: 200 Free Tutorials.
https://www.youtube.com/user/DrSassiLA/playlists

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