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PFtrack import questions

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dh2909

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PFtrack import questions

PostTue Dec 01, 2020 9:15 pm

PFTrack import question

I am new to external tacking software, I have been learning pftrack.

When I import the fbx into fusion, 2 things don't work.

1. The camera orientation is wrong and not pointing at the point cloud (can fix this using camera import and a maya file export)

2. The key frames for the camera movement always start at frame 1, but my clip could be further down my timeline. So there is no camera animation and moving my key frames to my current frame does not make the camera move.

The only workaround I have found to the 2nd one is to use the same image sequence I use in pftrack in its own timeline before entering fusion. Then copy that fusion clip to the main timeline. (I am using resolve not fusion standalone)

I'm sure there is a simple fix to this I am missing.

Any help appreciated
Thank you
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Bryan Ray

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Re: PFtrack import questions

PostFri Dec 04, 2020 7:03 pm

The FBX problem has existed for quite a while, and it's annoying, but it's only a couple of extra clicks, so those of us who use that combo of software have just gotten used to working around it.

I don't know if more recent versions of PFTrack than the one I have make additional export formats available, but Alembic usually works out of the box.

For the offset problem, there's a Frame Offset control in the export module that should do what you need. I've never needed it before, so I am not sure if there are any 'gotchas' to using it. Or in Fusion, you could select all the keyframes in your imported scene and use the Time Offset feature of the Keyframes view to move the keys to the desired frame. I have to do that all the time with Mocha tracks—the Trackers come in at the right frame, but the splines are usually at 1.
Bryan Ray
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http://www.musevfx.com
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dh2909

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Re: PFtrack import questions

PostSun Dec 06, 2020 10:01 am

Thanks for the response. Yes I have found using the alembic and frame offset a good solution.

What image files do you convert to for use in pftrack?

I have found if I use resolve to export as .tiff and use them in pftrack i get a really good track.

But if I use photoshop to convert to jpg I get a very jittery track.

The problem is file size. The tiff will come in at like 8gig of file space, and the jpg a few hundred mb.

Is there something I'm missing in my conversion that is causing jpg to be jittery?

Thanks
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Bryan Ray

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Re: PFtrack import questions

PostMon Dec 07, 2020 3:56 am

You're probably compressing too much. Jpeg compression creates artifacts at contrasty edges. But even at 100% a jpeg will still be compressed and much smaller than a TIFF, and thus faster to process.

I usually do track on jpegs at 85% compression at first. If I don't get an adequate solution, then I may switch to OpenEXR. We always make both formats during ingest of plates, though, so I always have them on hand.

I generally prefer to avoid TIFF because the specification is too loose. It's not unheard of to create a TIFF in one program that another can't open. I ran into that problem frequently in school—the files I created by Premiere on Windows at home wouldn't load in Nuke on a Mac on campus.
Bryan Ray
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http://www.musevfx.com
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dh2909

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Re: PFtrack import questions

PostSat Jan 09, 2021 8:35 pm

It turns out the jpg wasn't the problem. It was my poor tracking skill..

I had a few tracks that where jumping from one point to another that I had not noticed. This was causing the jitter I was getting.

I was using trim rather than removing the offending tracks
Once they were removed, the track was sound.

Cheers for the input
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Bryan Ray

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Re: PFtrack import questions

PostSat Jan 09, 2021 8:52 pm

I lean pretty heavily on the Acceleration Graph to spot those. Whenever you see a big spike in just one or two trackers, there's a good bet that it's jumped off target. Don't just use the trim feature in that graph, though, because it won't do anything about trackers that have picked up a new feature after the jump. Usually you'll want to delete everything either before or after that point in addition to the bad frame itself.
Bryan Ray
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http://www.musevfx.com
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dh2909

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Re: PFtrack import questions

PostSat Jan 09, 2021 9:20 pm

That is exactly what I have learned :)

I have got to point now where I can get some good accurate tracks, now I understand it better.

Do you know how to see the solve error after doing a refine? It shows solve error after initial solve, but doesn't update when refining.

Cheers
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Bryan Ray

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Re: PFtrack import questions

PostSat Jan 09, 2021 9:23 pm

Hmmm... No, I don't. I've got a tough track to do next week; maybe I'll remember to look for it.
Bryan Ray
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