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Start/stop Tracking mid clip?

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Rhys Sherring
Start/stop Tracking mid clip?
on Nov 9, 2017 at 7:16:10 am

So I've got a shot of a front door, and then someone comes and opens it, revealing someone on the other side. I can't figure out how to make a power window, that tracks the persons face, start at a certain point in the clip instead of simply right at the start, as well as its opposite: stopping it later in the clip before it finishes. It's permanently on through out the whole clip.

So far, I can't get key frames on the tracker window to do anything at all. I also don't know what the difference of 'Clip|Frame' is. May someone reveal these secrets to me? This is my first official day using Resolve proper haha.


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Tero Ahlfors
Re: Start/stop Tracking mid clip?
on Nov 9, 2017 at 7:40:37 am

[Rhys Sherring] "I also don't know what the difference of 'Clip|Frame' is. May someone reveal these secrets to me? This is my first official day using Resolve proper haha."

Have you tried reading the manual?


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Rhys Sherring
Re: Start/stop Tracking mid clip?
on Nov 9, 2017 at 8:18:46 am

Feel free to point out which page its on.


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Tero Ahlfors
Re: Start/stop Tracking mid clip?
on Nov 9, 2017 at 8:34:11 am

Feel free to use the index or the search function.


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Duke Sweden
Re: Start/stop Tracking mid clip?
on Nov 9, 2017 at 12:22:50 pm

Go have a cup of coffee, Tero, I'll handle this 😉

What I would do, as I learned here just the other day, is to use the razor to cut your clip at the point you want the effect to start, and then also at the point you want the effect to end. THEN, apply the effect to the part of the clip you want it, which would obviously be the middle portion of the clip.

Tero wants everybody to use the manual, but sometimes it's hard to word the search term.

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Michael McCune
Re: Start/stop Tracking mid clip?
on Nov 9, 2017 at 3:35:45 pm

Rhys: Regarding the Clip mode and the Frame mode, one might first understand that these modes refer the polygon or Power Window changes. That is, changes -- such as enlarging the polygon--apply to the entire clip OR they are applied to the frame only. Because Resolve will interpolate between frames, it smoothes out the frame changes made in Frame mode.

As a practical matter, I usually find myself capturing the object to be tracked (probably with the cloud option, or perhaps with the point option chosen--with a polygon window. Then start the tracking. (Usually I use the fewest of the options for Pan, Tilt, Zoom, Rotate and 3D, often just Pan and Tilt, for simple tracking in a 2D plane.)

I usually set the mode to Clip mode at the outset and then start.

It won't be long before the window drifts from the object. Of course if one's clip is only a few seconds then this drift issue might not occur. If is is minutes in duration, then it probably will drift.

When it drifts, I usually pause the tracking, using the pause button in the tracking window, and change the mode from Clip to Frame.

Look at the trace in the tracking window: when the track fails it usually shows a larger excursion and is fairly obvious. You might well use the tool in the tracking window to highlight and then Delete Selected Frames to clean up the track data path.

Then recenter your window on the target and recommence tracking. Rinse and repeat. This can be a tedious routine for long clips, to be sure.

This means that almost all of the tracking is done in Frame mode with lots of correcting re-do work.

With a window that basically captures and tracks your subject, then perhaps a filter applied to this limited polygon area might allow color adjustments to, say, a face.

Good luck! Mike


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Marc Wielage
Re: Start/stop Tracking mid clip?
on Nov 10, 2017 at 2:33:16 am

I agree with Michael's method (but I sympathize with Tero, who correctly points out that Tracking is well-covered in the manual).

I'll add that sometimes, ALL MANUAL rotoscoping is necessary, and you just have to play a few frames, stop, move the window, play a few frames, stop, move the window... all by hand until the shot is done. And then you have to change the window shape. And you may even have to change the window correction and/or softness. And you will probably have to check it multiple times. A lot depends on how perfect you want the results to be. There are many situations where auto-tracking (even Mocha) is not going to work.

I just had a case with a prison film where I had to lighten people behind prison bars, and I had to jump through a few hoops to figure that out. The trick was keying the prison bars and using them as a mask, which allowed me to illuminate the prisoners but not the bars. Every situation is different, everything is a challenge.


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Mathew Farrell
Re: Start/stop Tracking mid clip?
on Mar 22, 2018 at 2:51:09 am

Thanks for the inputs, guys.

That's a great tute for manually adjusting a tracking window, but I suspect Rhys is trying to turn it on/off completely. In his example, while the door is closed, you don't want that power window hanging around making a portion of the frame brighter.

There are probably a thousand ways to do this. I've settled on keyframing the window's opacity. That means opening up the keyframe editor, finding the right attribute (e.g. Corrector 2 > Circ Win ), and dropping static or dynamic keyframes at the points you want to turn or fade on/off your power window. With the appropriate keyframe selected, go back to the Window palette (middle control panel) , select the appropriate power window and change its opacity to 0% or 100% as required.

You might do this in conjunction with manually 'rotoscoping' the window, or more appropriately, changing it's shape with the tracker controls in frame mode, as Duke suggests, which would allow for the edge of the door covering the face for a few frames.

Mathew Farrell
flowstate.com.au


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Marc Wielage
Re: Start/stop Tracking mid clip?
on Mar 22, 2018 at 3:29:47 am

I find you have to change opacity AND the window shape in order to really make this work effectively. A lot depends on the specific situation: I had a case not long ago where I had to light an actor's face as they were peering out from an opening door. In that case, the window moved from being very narrow to being "face-shaped" as the door opened. It was amazing how well that worked, truly getting a keylight in a place where no keylight was really possible.

Tricks like this don't always work, but when they do, it's fantastic.

If I had to start or stop tracking mid-clip, I think the advice to manually cut it in half is a good strategy. You can always "undo" the split but retain the tracking afterwards, if you want to be a stickler on preserving the edit timeline.


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Mathew Farrell
Re: Start/stop Tracking mid clip?
on Mar 22, 2018 at 5:28:56 am

thanks Marc.

I'll agree that blading the clip is an elegant option in some ways, but I don't like it myself. It's just that little bit messier when it comes to changing grades, and an absolute no if you need to stabilise.

Mathew Farrell
flowstate.com.au


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