Suggestions for tracking 3D object with a static camera
Posted: 28 November 2018 10:55 PM   [ Ignore ]  
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What’s the best way to track a 3D object when the camera is locked down?

I watched a bunch of the Cineversity tutorials on camera and object tracking, but they all use a moving camera with good perspective shifts.

I have a truck in a test facility that’s on some sort of giant turntable that rotates it front of a static camera.  I want to track graphic elements to some features on the truck.

The sequence is here (my source was for testing, somewhat compressed):

http://marshall-arts.net/Support/CascadiaFrontWind.zip

I used the Camera Calibrator to try to establish a Focal Length and basic orientation, and the result seemed close when I dropped in a 3D object.

I dropped some manual trackers on the wall, ran a manual track, then used the 3D solver in Nodal Pan mode with the focal length set to what the Camera Calibrator came up with (39.755).  I’m guessing nodal pan is what I want in this situation.

The resulting Solved camera was pretty wonky, and adding planar and vector constraints didn’t seem to help getting it lined up to the “real world”.  I thought a plane object aligned to the planar constraint would line up in perspective, but I couldn’t get it close to matching (whereas the Calibrated camera produces proper perspective on the walls).

Do the various constraints not work in Nodal solves?  If not, is there any way to get the scene oriented somewhat correctly to the real world?  In this case the camera should be low and looking up.

I went ahead and 2D tracked some features on the truck (roughly supervised), ran a 3D solve, and got some useable nulls in 3D I could attach my graphics to.

Any suggestions?  I still can’t seem to get attachments to work, so here’s the scene file:

http://marshall-arts.net/Support/TruckSetup.c4d.zip

Thanks.

Shawn Marshall
Marshall Arts Motion Graphics

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Posted: 29 November 2018 09:23 AM   [ Ignore ]   [ # 1 ]  
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Hi Shawn,

The answer is quite simple. You have only to think a little bit out of the box. Having said that, just track the truck only! Exclude all tracker that do not belong to the truck. In this way the camera will stuck to the truck, like a selfie stick. (…the truck would be static, and so the camera moves).

Since the footage will be on a background object, it will stay in place. All tracking points, after they are solved will represent (if correct, there is a lot of reflection in this shot, that will require to evaluate each tracking point!) a position on the truck itself. Place anything where you need it. Done. Just to be clear: NO OBJECT Tracker object is used at all.

Screen capture
https://www.amazon.com/clouddrive/share/nvaxomF8rnjm82V3S0whSumBQb2XATFI6nqukfbPZEK

If this concept is clear, adding a light to the scene should be done under a Null object. This Null object is Constrained to the Camera. So the change of the truck will show up with the change of the shadow on the object.

All the best

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Dr. Sassi V. Sassmannshausen Ph.D.

Photography For C4D Artists: 200 Free Tutorials: Texture, Panorama, HDRI, Camera Projection, etc.
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Posted: 29 November 2018 10:45 AM   [ Ignore ]   [ # 2 ]  
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Thanks for the direction; I appreciate it.

I see you have some sort of constraint on your Motion Tracker object, but I can’t tell what that is.

Did you run an auto track on the whole frame and then delete all of the tracks that weren’t on the truck?

Best.

Shawn

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Posted: 29 November 2018 10:53 AM   [ Ignore ]   [ # 3 ]  
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Hi Shawn,

You can download the clip, it is in UHD. Anyway, the constrain is just a Vector Constrain, to get some sort of scale into it.

Yes, typically, I try the automatic first, just to get familiar with the shot. Often I place more tracker on the end and the middle and track again from there. In this shot I deleted all “Non Truck Tracker” and found even later some that I missed, they followed reflections (Blue arrows). However, some manual trackers are inside, and I have supervised those. I checke each frame, and adjusted those who slipped.

There were quite a few on the truck that have no value. Check carefully, even the algorithm is very able to spot those, you get better results by deleting them from the start.

(I had no lens profile and no survey data. I guess you have even much more frames. The Camera Calibrator tells me a 28mm lens, but the Motion Tracker concludes more towards 17mm, given a 36mmx24mm sensor. You have certainly more data.)

My best wishes for the project.

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Dr. Sassi V. Sassmannshausen Ph.D.

Photography For C4D Artists: 200 Free Tutorials: Texture, Panorama, HDRI, Camera Projection, etc.
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Posted: 29 November 2018 11:41 AM   [ Ignore ]   [ # 4 ]  
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Thanks for the details on your workflow.

I know almost nothing about the shots I’m being sent.  Fortunately we have some leeway on these kinds of graphics, so I don’t have to be super-precise.

Best.

Shawn

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Posted: 29 November 2018 12:00 PM   [ Ignore ]   [ # 5 ]  
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You’re very welcome, Shawn.

Yes, I have heard that only too often, people shoot stuff, then request to get anything done with it. A few measurements from the set, and a lens chart, shot in a similar distance setting than during the shot (lens breathing!), the camera model as well the used sensor size (that can vary, e.g., RED). Perhaps a MacBeth chart, etc.

Each tracking shot has something specific to it, so it might be always advised to stay creative.

As a side note, if you have to attach only “decals” on the truck, perhaps Mocha Pro might be a faster way.

ENJOY.

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Dr. Sassi V. Sassmannshausen Ph.D.

Photography For C4D Artists: 200 Free Tutorials: Texture, Panorama, HDRI, Camera Projection, etc.
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Posted: 29 November 2018 02:44 PM   [ Ignore ]   [ # 6 ]  
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I’m finding the tracking workflow on Cinema 4D to be fairly intuitive.  The Cineversity tutorials are very well done.

I’ve had Syntheyes for ten years or more, and we just spent $500 to upgrade it for this project, but I don’t find it to be very user-friendly, even after watching a ton of tutorials.  Perhaps it can handle super-complex shots that C4D would have trouble with, but for the kind of stuff I’m looking to do C4D is working well.  TBH, I kind of dismissed C4D until now since I figured its built-in motion tracking functionality would be lacking.  I didn’t even know it could do object tracking until a week or so ago.  Obviously I’m not asked to motion track stuff that often.

I just did another truck rotate shot, and it only took ten minutes or so to get a useable solve and 3D scene to bring into AE.

I have some other shots with moving cameras and objects which will require graphic enhancements, so I might be asking for some more hints.

Best.

Shawn

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Posted: 29 November 2018 02:58 PM   [ Ignore ]   [ # 7 ]  
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Yes, Shawn,
Syntheyes has grown a lot. However: Since the C4D options are so integrated and easy in use, yet reliable, I have lost a little bit track of Syntheyes to be honest (I keep it up to date, though). I took a lot of courses back in time at PXC and FXPHD about all kind of tracking apps. Before that – In the late ‘90s things were more cryptic and often nothing more (or less) than an University project, like the later known PF-Track, which was back then free to download.
Having used many of these by now for a wider variety of projects, I like auto-track with the option to manually refine things, including a complete lens workflow.

When Dr. Steve Baines show-cased his ideas back in 2005 during our PXC London meeting his ideas about tracking, I wasn’t aware that we will have it today his ideas so wonderfully integrated in C4D.

Yes, as long as I have an idea how to tackle a shot, I will share my collected knowledge of course. Just let me know.

ENJOY

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Dr. Sassi V. Sassmannshausen Ph.D.

Photography For C4D Artists: 200 Free Tutorials: Texture, Panorama, HDRI, Camera Projection, etc.
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