I loathe and love the gmask tracer

First, the Gmask Tracer is so good and so far underappreciated as a keyer. I don’t know how it does it, but, it is incredible. It’s super intuitive as a keyer and I can’t believe how good it is and how its saving my bacon. Again.

BUT. Why do the Gmasks in the Gmask Tracer absolutely freak the feck out seemingly so often and with such ferociousness? I musts have spent hours over the past week or two deleting crummy keyframes and hitting Snap, Set, Analyze over and over and over again. Hundreds if not thousands of times.

When I use Mocha and do shape tracking there, guess how many times their masks freak out so bad that you have to zoom out and delete a bunch of keyframes and snap and hit all the buttons? Zero. Not a single time in probably a week of mask making. In fact, it’s so good I’ve done a ton of roto and probably couldn’t even tell you how to delete a keyframe in Mocha. It. Just. Works.

Hence, the loathe/love relationship.



Hi Randy,

If we can get repeatable steps, we can log this quickly and get the team to look at it.

The most difficult task is searching for something that never “appears” to happen for us.

Not diluting your pain in anyway, I’m just showing a bit of light at the end of the tunnel :relaxed:

Hope this helps!



One of the things that I find makes my masks go south is that when you do a track for just part of the duration of the shot, the shape channel extrapolation is set to linear, even if you have your preferences set to constant. I am frequently resetting the extrapolation so that I can continue to manually adjust keyframes beyond the beginning or end of the track and I’m not fighting against the tracker.


Yeah i find the Gmask tracer so hit and miss. Sometimes it works amazingly well and other times it just freaks out at a slight bit of movement or a slight bit of occluison

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It’s less repeatable steps and more behavior. It feels like there’s an algorithm somewhere in the gmask tracer that if a shape changes more than a few percent it should stop. Instead a couple of crazy key frames and boom its off the rails and extrapolating linearly and requires deleting key frames and changing extrapolation constantly. Or at least give me some kinda warning or indication Instead it changes shape so quickly and extrapolates linearly and is a ton of work to wrangle.

Let me see if I can screen record what I’m talking about. Maybe I don’t know how to use the tool correctly. I guess I’ll find out.


I have to agree with @randy 90% of the time I try with a tracer, it goes bonkers and I revert to good ole’ Gmask. Gets the job done, crudely but fast. Once in a while, it works as intended.
Another comparison: the planar tracker in Resolve is very no fuss, gets it done quickly. Gmask tracer is fussy as hell.

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A lot of the time so get terrible results it’s to do with high values. If I convert to r709 and clamp if often behaves better. Same goes with grain so de graining helps. Sometimes using the tolerance helps. And sometimes using the the other thingy where you choose how many points it tracks helps (forgot the name of it).


I haven’t tried Mocha. I would imagine that it is good. Isn’t it a stand alone tracking software?

I have access to Resolve and Nuke but so far my ventures into these have been for alternative time-warp options more than tracking. Oh I do all of my lens distortions in Nuke but I am getting off topic slightly.

When the new planar and perspective grid tracking came to flame I was so happy. Maybe easily impressed because of not having had planar tracking before, it was just so helpful.

I have mentioned before about how I threw perspective grid at everything I could. I got used to its quirks and I loved the way I could edit my hold out splines to focus on certain areas. The planar tracking in gmaskTracer was another welcome addition. Realising that you can use a dummy spline to get the axis track. One where you can change the shape of your spline as you go, has helped me nail some tricky tracks.

More recently (thanks @kirk ) I have been emboldened to use the Camera AnalyzerMono more and more
and I have been getting fairly accurate results.

I don’t disagree that it has its quirks and I am sure that if I had Mocha or something else to compare it to I would see how much they differ but this is what I have got and having this has improved my comp life so much that I find it hard to complain.

@zorrofx I would be quite happy to loose the Gmask (legacy) all together

@johnt Not doing your tracking in scene linear helps immensely.

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This delights me!

I will still use the legacy gmask for a complicated shape. Its speed of drawing masks is yet to be surpassed.

Also with the tracer can adjust the points manually and that will apply to the object I apply it to like new artwork on a wall? I can do that in with the perspective grid but can’t seem to for the tracer? Is that correct?

Hi Ben,

That is correct. The Gmask Tracer spline is not a warping tool.

If you adjust a point in the spline, you are adjusting the mask with no effect on the image you are working with (like your artwork example) The mask is either holding out or cutting a shape with your image.

The perspective grid is a physical 3D object and when you attach images to it, you are able to bend your artwork along the perspective. Adjusting the perspective points will adjust the attached image.

Hope this helps.


I guess i can still do that with the perspective or bi cubic on the image but it would be nice to do this all in the planar as i can then get a good stabilized plate to work with.