Mocha Tracking on a Stabilised Layer

Hoping someone might be able to shed some light on this as I’ve never quite worked it out. Is it possible to mocha track a shape when viewing through a stabilized layer? I’ve never been able to do it without the shape going a bit haywire.

I often apply a 4 point track (imported from Nuke) and apply to that a layer and view that stabilized to do roto on. (Generally this iscamera track data to stabilize the plate at a given depth)

Then I would like to be able to create another layer, draw a shape and then mocha track something that is moving independently from the camera within the stabilized view. Then when I turn off stabilized view the shape is good, tracked with both my original point tracks and then the mocha track on top and then any manual keyframes can be made.

Is this workflow possible in Silhouette or is there a specific layer hierarchy needed at all I’ve never realised?

Thanks guys.

Inside of your stabilized layer, create another layer and inside it, create the shape you want to use to drive the Mocha tracker. Your layers and shape should look like this:
image

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Hi Marco, just coming back to this post.

Correct me if I am doing something completely wrong here but I have always tried to do that exact layer hierarchy but when setting the viewer to the stabilized layer and then attempting to mocha track the layer inside it, the shape always goes haywire for me and does not stick to the plate at all.
Katie’s FXPHD “Introduction to Roto & Silhouette” lesson 5 course also touched upon this concept however she used point trackers and applied them to the layer inside of the stabilized layer. I tried this which worked quite nicely but when Mocha tracking it doesn’t seem to work in the same way?

What I did find however is if I view the stabilised layer and then mocha track a layer which lives outside of this stabilised layer that tracked nicely. But my question is then, is the mocha tracker being assisted at all from the stabilisation track in that case or is just in the viewer for my benefit?

Cheers,
Josh

@joshbarham With the footage I am using, I can use Mocha for the stabilize and another Mocha layer for the additional track.

In your example below, the stabilize has no effect on the Mocha layer outside of the stablilize layer.

I am not sure if this will matter, but when you stabilize, make sure you don’t choose Active Layer. Select the actual named layer instead.

I can do a remote session on my machine and show you with my footage if that would be helpful.

Hi Marco,

Returning to this topic again as I never actually solved this issue and it repeatedly pops up. Using the layer stack you showed, when attempting to mocha track on the active layer inside the stabilised layer the shape does not follow the stabilised object in the viewer.

Using v7.5 by the way. Happy to do a remote session if thats easier

Also something else I tried @marco. I rendered out the stabilised plate first and then imported this into Silhouette. Then was able to mocha track as normal the object in question.
But then I rendered out the mattes and brought them back into Nuke. I would expect to simply be able to reapply the matchmove data to the rendered alpha, with the same reference frame, and it will then match the original plate. But it doesn’t, it is not even close?

Am I doing something fundamentally wrong here or missing something?

Cheers

Sorry one other update I have. I have just realised (and remembered from a similar issue in the mocha forums) that the bounding box, or windowed EXRs as it was called can cause problems.
So I reformatted/cropped the stabilised plate back to the original plate format (no cropped/animated bbox at all). I then rendered, imported into Silhouette and did the roto on this plate and then rendered the matte, brought it back into Nuke and reapplied the matchmove and matched up perfectly!

So I guess the question is, why doesn’t it work when using a stabilised track live in Silhouette and then mocha tracking ontop of this. Is it this bbox/format issue happening behind the scenes when stabilsiing causing misalignments perhaps?

Sorry for the multiple posts. Cheers!

@joshbarham Doing some tests now. Will update shortly.

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@joshbarham So, it appears that tracking a stabilized source only works when using point trackers in the stabilized layer. The Planar and Mocha trackers always track the original image/mask. We will need to make some modifications for this to work with the Planar and Mocha trackers.

Here’s the setup that will work when using Point trackers.
image

Tracker - Stabilize Source is the initial track used to stabilize the image and was applied to the Stabilize layer. The Viewer was stabilized using the Stabilize layer. Two additional Point trackers were placed in the Stabilize layer and tracked an object. The two Point trackers were applied to the nested Match with PT layer.

Note: The Planar and Mocha trackers could also be used instead of Point trackers for the initial stabilization.

Thanks for the update Marco, good to know. Yes I alluded to Katie’s FXPHD “Introduction to Roto & Silhouette” lesson 5 in an earlier post which showed this concept with point trackers. I was wondering why it wasn’t working with mocha.

Not sure if related or a completely seperate issue then but importing a stabilised EXR sequence (with an animated bbox) into Silhouette appears to playback differently (its like the entire format moves in an incorrect way) which then causes roto done on this stabilsied plate to be offset and positioned incorrectly when bringing back into Nuke. I had the same issue when importing into standalone mocha too

It isn’t working in the Planar or Mocha trackers because they are always using the original image/mask to do the tracking and not the stabilized version.

This is a completely separate issue. Variable size exr’s can be tricky to deal with the constantly changing DOD. I suggest comping it over the original or colored background so that the resolution is constant.

Will do, yes having a constant resolution does the trick.

Thanks Marco for all the help here. Very much appreciated