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Motion Tracker
Posted: 12 April 2017 05:25 PM   [ Ignore ]  
Total Posts:  6
Joined  2015-10-11

Hi everyone,

I’m trying to learn the motion tracker and have followed a few tutorials covering automatic and manual tracking. I’ve attempted to track a flyover (6 times now haha) and doesn’t seem to be woking right for me. The footage I am testing is the beginning of this public domain footage:

https://pixabay.com/en/videos/coastline-beach-city-usa-sunset-3581/

In the attached jpegs I have enhanced the lines so you can see where my planar constraint (set to Y green) and 2x vector constraints (X red and Z blue), it seems to be working to a certain degree but its like the X axis is off even though I’m telling it to constrain to the vector constraint set to X that I had created. You’ll see the world grid X doesn’t quite match it, I’ve included a screenshot with the world grid turned on with a couple of cubes placed in so you can see my issue, I also have some sliding issues of the cubes.

If you think I need to upload my file let me know, I’d need to remove the footage though as its way to big to upload to Cineversity. Any suggestions where you think I might be going wrong or links to any appropriate tutorials would be appreciated.

Cheers

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Posted: 12 April 2017 06:24 PM   [ Ignore ]   [ # 1 ]  
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Hi braincell creatives,

I did a quick track with it and it works. Normally I would set some manual trackers in the area of the projects main interest.
https://www.amazon.com/clouddrive/share/Cce17S71lzhAPmdSgNfQNlllQcljpwJADpjQok9yeKn?ref_=cd_ph_share_link_copy

This is off-topic, but to protect the people in this forum: It looks like “sUAS” footage. If so – So, no footage included in my file. For private educational purposes it might be OK to use it, but even then I have a very uncomforatable feeling about it, but please note that the footage might violate FAA rules, so far I can see it, be careful if you like to publish it. Perhaps ask them to provide the FAA-Authorization for the Class B Airport KSAN for example, or a Waiver to fly over people [FAA 107.39], and the RPIC license (Part 33 or 107 - otherwise you can’t even use those as commercial, as advertised, YouTube ads included! Seriously, that can cause a lot of trouble. Sorry about the alarm: … just trying to keep everyone safe here.)
https://goo.gl/maps/CMU9WgMdpfL2

Have you set any origin point (Position Constraint?)

Have you set all scene file settings (project and render) to the footage specifics, fps, pixel-ratio, and resolution, e.g., 250 frames max.
Note that the footage has some lens distortion, and a C4D scene has none by default. Take the front line of the buildings from left to right, it is not a straight line.
Lens distortion means, that the tracking points move slower or faster based on the lens, not on the given geometry of the buildings for example. Since these buildings are in the foreground, where the tracking should have its best precision, errors might occur.

Rule of thumb, especially for the green triangle Y, the further the points are away, the less precise they are. The more they are in the background the less likely they are to be useful at all, for many reasons.

Have you look at the side/front view, are all elements are plausible? It is nearly a flat plane to track and the camera move is more like a dolly, does this resemble in your side/front view.

While you set up the Y triangle, make sure that all points you use are in the same Y area, equally high, not one story and the next three stories, can you even see that way back in the frame?

I guess I don’t have to mention it, but the waves shouldn’t have any tracking points at all, nor cars or people, clouds, etc. Those trackers need to be deleted instantly – before the 3D solve.

Where objects are located in Y needs to be based on the scale (know length…) that you have set up for this scene.

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.
https://www.youtube.com/user/DrSassiLA/playlists

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Posted: 12 April 2017 07:13 PM   [ Ignore ]   [ # 2 ]  
Total Posts:  6
Joined  2015-10-11

Thanks Dr. Sassi,

I’ve downloaded your scene file and initially looking theres much less sliding - I’m going to take a look at your constraint placements etc… and compare to my file.

I had inserted a position constraint as well. I’m wondering if the lens distortion isn’t helping with the X axis in the lower part of the footage especially when I place a cube in that area. I see you’ve got a lot more tracking points than I had so I’m going to try again using the auto track and mask out the sea.

Yep, this is just for learning purposes. Will let you know how get on.

Cheers

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Posted: 12 April 2017 07:26 PM   [ Ignore ]   [ # 3 ]  
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Yes, it has a learning curve, braincell creative.

But whatever you do, there is no short cut that replaces the lens distortion workflow. It will never give a great result if the footage to track has some or even a lot of it. The results created based on the undistorted practical footage shouldn’t be used for the final compositing, as any movement of a pixel, more or less than full pixels in distances, will limit the quality of the result. Since 3D rendering are mostly too sharp, and practical footage often blurry (I do not suggest sharpening the footage here, not at all! This is a process on the very end of the VFX/editing pipeline, if at all.) The typical workflow is to distort the 3D rendering to match the original footage to gain the best quality. If the practical footage was retrieved from a 6K or 8K source (talking about UHD as delivery) with good lenses, then it might be advised to render the 3D in at least in 5K, and if needed with the required padding to have what the original image needs to get covered.

Since the distortion is different in each part of the frame, objects moving though it will move with a changing speed, and that can’t be compensated with anything other than described above. The tracking algorithm tries to understand what is going on, but the results on top of it are not really what one should use, given a strong distortion
https://www.amazon.com/clouddrive/share/olabEDm8cGLXQodTw786oxZa6LtfigMLnKUMAy7bgMh?ref_=cd_ph_share_link_copy
To see how the green line in the image should be:
https://goo.gl/maps/CMU9WgMdpfL2


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.
https://www.youtube.com/user/DrSassiLA/playlists

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