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Workflow for area tracking

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Montaire

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Workflow for area tracking

PostMon Jul 27, 2020 9:08 pm

Hi,
I have to track a military helmet before a background with dirt and leafs which has almost the same brightness and color as the helmet, so I can't really use any kind of keying.
As the actor rotates his head, the object changes its shape.
First I tried to use the Planar Tracker as an area tracker but obviously this tool is not for that kind of application.
After that I tried a Polygon Mask, with trackers, but the tracks drifted, due to the rough texture of the dirt and the clean texture of the helmet.

Do you guys know any good solution in Fusion for this kind of problem?
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Kel Philm

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Re: Workflow for area tracking

PostMon Jul 27, 2020 9:55 pm

Why are you tracking it, how long is the shot? This may determine how you can approach the issue. My gut tells me this may be a manual roto job.
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Montaire

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Re: Workflow for area tracking

PostTue Jul 28, 2020 7:19 pm

Thank you for the quick response!
I was afraid that this will be the way to go.
It goes trough 3 takes, around 750 frames in total.
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TheBloke

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Re: Workflow for area tracking

PostWed Jul 29, 2020 6:15 pm

Have you experimented with manipulating the image before trying to chroma key it?

For example, converting it to HLS or HVS spaces with a ColorSpace node. Even if there's no difference in RGB colour or brightness, there could be a difference in saturation or some other area that might not be immediately visible to the naked eye. It's worth a look at least.

VFXStudy did a good video on it which will show some possible techniques:


I'm not saying it will work, but it's something to test out before resorting to manual roto. It's possible it might at least get some of the way there; eg it might give you a key that selects 50% of the object, or selects 100% but with some holes, and then you need to roto the remainder. Which could prove to be less work than rotoing the whole thing.
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Sam Steti

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Re: Workflow for area tracking

PostFri Jul 31, 2020 9:43 am

Hey,

Obviously, you have to isolate the object by any possible mean, as you had understood. I'd personnally also try the HSL way as shown in Bernd vfxstudy clip if the clip is too long to roto; but you may also make a rough matte inside which you use a luma keyer node, a filter node or whatever can isolate at least the edges of the helmet.
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Jason Conrad

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Re: Workflow for area tracking

PostSat Aug 01, 2020 6:50 pm

750 frames doesn't sound too long to roto, but 3 takes does. I mean, I'd do it without complaint for a price, but I'd be silently questioning the wisdom of whoever paid me to do it. Unless maybe the three takes are in different languages?
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Montaire

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Re: Workflow for area tracking

PostTue Aug 04, 2020 7:29 pm

Thank you all for the help!

Sadly the HSL method not worked out well. I could only better separate parts from the helmet with it.

As last resort I did the masking in Blender, and imported it as a black and white sequence.

There I could make masks for the individual tracking ponts, to track only the edge of the helmet, and then animate the mask relative to the tracked points as well where needed with only a couple of keyframes.

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