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  1. #1
    Join Date
    Mar 2012
    Posts
    2

    Default Tracking points- access to raster space/post transform co-ordinates

    Hi all first post - am fairly new to Nuke.

    I\'m tracking an image to a page of a book using gridwarp (linked to tracker points), which is working fine - there\'s a post camera move on the comp (via a basic transform), again, no problems yet - however I need to resolve the comp back to full-screen raster space to match the shot. Problem starts here.

    The issue being that I cannot access/control the position of the gridwarp in pure \'global\' raster space, as the transform node affects the co-ordinates. Is there a way to do this? (Not using 3D space BTW just 2D)

    I was hoping to set up a simple user knob to blend between the values of the tracked points and a \'dummy\' track fixed at the corners of the raster image - but as the gridwarp is being passed through a transform node, the results also have the transform applied.

    I\'ve had to just do it by eye at the moment, but unfortunately this is going to be needed to be performed on a large number of shots, and so a simple way of blending between a tracked and transformed grid (local space) and the global raster space would be ideal.

    Am I attempting something that cannot be achieved?

    Newbie in \"first post nightmare\" shocker...
    Last edited by Levi3d; 20th March 2012 at 01:23.

  2. #2
    Join Date
    Jun 2011
    Posts
    18

    Default

    I think in your attempt to make it very clear what you\'re trying to do, you\'ve made it seem a little more complicated... Haha, that\'s alright though (I do the same all the time!)

    You can try applying an inverted version of your original transform, and then another transform right afterwards (as long as they are one after another they\'ll concatenate and there should be know double resampling). To make it a little more streamlined, you can link the original transform to the inverted one, so any changes you make will ripple through.

    Hopefully I answered your query..!

  3. #3
    Join Date
    Mar 2012
    Posts
    2

    Default

    Quote Originally Posted by colton View Post
    I think in your attempt to make it very clear what you\'re trying to do, you\'ve made it seem a little more complicated... Haha, that\'s alright though (I do the same all the time!)

    You can try applying an inverted version of your original transform, and then another transform right afterwards (as long as they are one after another they\'ll concatenate and there should be know double resampling). To make it a little more streamlined, you can link the original transform to the inverted one, so any changes you make will ripple through.

    Hopefully I answered your query..!
    Cheers for the answer Colton. I think I\'ve made it complicated because (I think - newbie don;t forget) it is... I\'ll try to to simplify it a bit.

    I need to be able to either

    a) Read the position of a tracked point after it has had a transform applied to it (as the value of the position in the track node itself doesn\'t change)

    or

    b) Write an expression that takes the (curve/keyframe) value of a tracked point and applies a transform (trans/rot/scale) to it within the track node, so I can access that value.

    Is there a way to write an expression that applies a full SRT transform to a points position?





    Hope that\'s a bit clearer?
    Last edited by Levi3d; 20th March 2012 at 23:29.

  4. #4
    Join Date
    Jun 2011
    Posts
    18

    Default

    You could have the transform\'s value effect a single tracker\'s position, or the tracker node as a whole in its transform tab for matchmove/stabilization via an expression (I think this may be what you\'re looking for).

    If you hit the equals sign when in a text field it\'ll allow you to input an expression. What you\'re looking for is probably \"curve+Transform1.translate\" (it could be Transform2, or 3, or whatever you have named your Transform node). Nuke will automatically resolve if it is for x or y translation (you can do this manually as Transform.translate.x or y though). This will add the value of the transform node\'s translation attribute to your current animation curve. Whatever edits are made to the transform node will travel downstream to your tracker. Hopefully this helps you out!

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