Blackmagic Forum

I have a planar tracker that tracks fine automatically for a few frames but then gets messed up. When I go to the part that got messed up and move the planar tracker's search area, it changes the previous frames that were tracking correctly. I have tried adding manual keyframes to the part I edit but it still changes all the frames before the point that I'm editing. How can I resume editing from the part that tracks incorrectly (in the middle of a clip) so that it doesn't move around the tracker from previous frames?

I believe this is similar to mocha where the spline you use as a search area and the actual track are not bound to each other. Meaning you don’t screw up the track if you move the spline to a different location it will simply append to the previous track like an offset.

For example, you might try to track the camera movement with a blurry object on the left side of the image. This works fine for the first few frames but then an actor walks into the image and occludes the object you’ve used. Now, before the track slipped you should place your search area to the right side of the image and continue your track.
The planar tracker won’t care that the search are has changed it simply records the pixel movements now from this part of the image.

(At least I’m almost sure that I’ve worked like this before. I hope I’m not mixing up fusion and mocha in my head)

Unfortunately I think you are getting Fusion's Planar Tracker mixed up with Mocha. Yes Mocha's search area and track are separate and can be linked and unlinked in various ways but the Planar Tracker in Fusion is crippled by a major lack of features. There is no manual adjustment possible as far as I can see, even though the manual suggests that there is, I quote,

TIP: The Set button lets you supervise a Planar Track in progress and stop it if you see it
slipping, making adjustments as necessary before clicking Set at the new frame to set a new
reference before continuing to track forward towards the end of the clip.

when I have tried this I am greeted with the warning, 'This will delete all tracking data and splines', Tracking cannot begin from an untracked frame without setting a reference either, so leaving a gap between tracked frames does not work.

Nah, this definitely works how I remember. And how mocha works, too. Fusion just makes this less obvious, but here is a quick demo:



There is no manual track mode like in mocha but the basic tracking is the same. The mask is only the search area, it does not in any way modify the track and you can change the search area even in the middle of the track.

In addition: just don't set a new reference frame number, because that will delete the tracking data just like it warns. (that's not an English sentence is it?)

Ah, right enough, I'll give it a go. He didn't change the shape in that example and it was as basic a track as is possible but moving the shape certainly didn't displace the track. I'm curious now what happens if the shape is altered and moved.

UserNoah wrote:Nah, this definitely works how I remember. And how mocha works, too. Fusion just makes this less obvious, but here is a quick demo:

There is no manual track mode like in mocha but the basic tracking is the same. The mask is only the search area, it does not in any way modify the track and you can change the search area even in the middle of the track.

Thank you, it makes sense now that it only uses the search area and not the actual track. Sorry about all this, I'm still a beginner, haha. I wish they had a manual tracking mode of some kind. Is there a manual tracking mode in a different tracker (besides the planar tracker)?

You can modify the paths that the standard tracker tool generates. If this is a case where you don’t need the planar tracker than you probably should utilize the standard tracker anyway.
The planar tracker is good for certain situations but it’s not the “one to rule them all” tool many people want it to be.

You can also use a transform tool after the planar transform to adjust slight slipping. Or in cases where more is needed you could use a grid warp. But that can get quite tedious and a good match move by hand is quite difficult.

So if you just need translation, rotation, scale then you probably get better results with the tracker tool.