Matte Clip - The real problem

Let’s talk about serious things.
We need a better understanding about the Matte Clip option. There’s multiple topic about it and none have an anwser (c.f. Matte clip).

Here is the problem :
We know how to import matte clip, but the way it works is just off. Let’s demonstrate that.

In this case I have a roto shape clip from a hand I just imported in Mocha.
See 1.

And I make my track shape on another layer, just below the matte clip.
See 2.

But as soon as I turn on my matte clip, instead of just exclude my track mask (as it should normally do with another track mask just above it), It just put the track mask as the invert of my matte clip and doesnt even care about the track mask…
See 3.

So what’s the problem with matte clip ?
How to use it like this correctly ?

Kind Regards

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Watching this topic :eyes:

Had exact similar problem , mocha Quick Tips: Export and Import Mattes on Vimeo is not clear.

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Hi @Saku
I’m sorry that you hit this issue. So yes, there have been some problems with matt clips in some versions of Mocha. Can you specify what build are you currently using? Its under the Help menu

Hello @elizabeth.postol,
I’m running Version 9.5.6 build 120.gd4552689308d
Build Date Feb 13 2023

Matte clips visualization is going to be fixed in Mocha Pro 2023. The release is coming very soon!


Thanks !
After 9 years of existence (as far as I saw here : mocha Quick Tips: Export and Import Mattes on Vimeo) this will be finally fixed !

Can’t wait the update

So, the new update just released yesterday and as we saw in the Release Notes :

MO-12058 Tracking a layer shape with a Matte Clip does not exclude any mattes for layers above

So we were happy to test that.
And surprisingly, it works… but not 100% correctly.

Ok, if we IMPORT our roto as a new clip and use the correct clip frame offset, we have our roto moving and then we can use it as a matte clip to exclude others layers. Great !

BUT, if we use the INSERT LAYER instead, the roto is not animated at all. In fact, I think the clip frame offset might be the problem because I have only the first frame of my roto (and the clip starts at 1001)

PLUS, the INSERT LAYER method doesnt show any track matte (using IMPORT method it works)
this is showed in this gif below (click on it to play it)

But the import method is more painful than the insert layer because it forces you to export your roto into a new render file.

Can you do something about this ?

Can you please clarify why would you want to use insert layer as a matte clip? What is your goal at the end?

Matte clips are expected to be used with rendered clips/sequences. If you just want to exclude some region from tracking area, you don’t need to render/reimport it back to project. You just need to place the exclusion layer on top

It is because I want to use matte clip like this :

Be able to do the roto in nuke and just import it in Mocha using the insert input and not having to create a write node and export the roto into a sequence.

I see now!
Adding a FrameRange node with the values that matches the frame range of the project should fix the static frame issue.

That said, Importing Matts via Insert input still seems to be an issue tho. This has been reported as a Bug now. In the meantime, I have to recommend you rendering Matte Clips as sequences.

Thanks for highlighting this and sorry that you hit this bug.

Thank you to report that at the dev team !

and thank you for your support about this problem !
I hope this will be usefull for future artists.

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Using the insert input like this is neat, but I think we could improve the workflow by adding some Nuke-specific functionality into Mocha that exposed the different layers from the input clip as different clips in Mocha. Then you could place your roto in the mask layer (or any custom layer) and Mocha would make it available for any purpose. It looks possible to do technically, using a similar interface to the one we use for stereo support in Nuke.

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