View Full Version : MatchMove scene - 3D mask possible?

12 December 2010, 09:29 AM
I've tracked a shot in and set up the scene in Nuke, I've then used the smae camera in Houdini for a snow man that I've created. Upon importing the exr sequence into Nuke, I now need to introduce a mask to the scene as the 'snow man' is supposedly outside, meaning I need to mask the window frames.

The problem is, I need to mask a 2D element, in a 3D scene.

Any ideas? (Hopefully this makes some kind of sense).
Thanks in advance.

12 December 2010, 10:37 AM
If the windows are in the footage then you can match a polygon plane (in Houdini) or a 3D card (in Nuke) by placing the card in the correct 3D space. There might be 3D trackpoints created from the matchmove which you can use to position the card.

Once you've positioned the card and assuming it doesn't slide around (if you place it in the wrong position then it will slide) then you'll probably need to add a rotoshape to it in order to finetune the mask on the window - in which you'll only need to make minor tweaks as the primary movement will come from the matchmoved camera.

Although this technique can often be used to do rough masks for quickly getting out composites, most feature film work still have 2D roto done.

You could also potentially just do a 2D track on the window and use corner pinning to create a mask which matches the window.

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12 December 2010, 10:37 AM
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