Tracking and global movement

[matt-lewis]

I have a space portal shot where I have to have the space background drifting in the background. This requires
transformations along the X, Y and Z axis. To complicate matters, the portal footage has camera jitter that I have to match to. When I try to track the space background footage to the portal foreground footage. The tracker overwrites all the X, Y drifting movement, rather than merging the data, so the footage no longer "drifts" but just rotates. I have tried to work around this by rendering out the "drifting" footage and then trying to retrack the jitter to this but it ends up jumping the footage around and not matching it the jitter at all.
Is this a limitation of the tracker? I have heard other trackers have a global parameters that allows you to maintain
the camera jitter tracking data in this case, but still make global x,y,z changes to the entire layer.
Any sugestions ?

cheers

[svensven]

The tracker can't "add" transformation, as far as I know, but you can create another level of layer hierarchy and apply the separate transformations to the additional layer.

You can track the "jitter" translation onto the space layer, then use Nesting to create another layer to put the "drift" translation on.

First, do your jitter tracking on the space layer. Then, select the space layer, choose Object>Nesting..., pick the Selected Layers option and hit OK. Now select the Nested Layers (or whatever you named it) layer, and do the drift transformations.

Good luck.

• Brian Demong, combustion instructor, Mesmer Animation Labs

[indus-guy]

This is less a tracker issue and more a compositing one - basically, you need to apply two sets of transform data to one layer, and it doesn't really matter whether the data comes from the tracker or is animated by hand. The suggestion to nest is great, I'd also add that you can parent the "drift" space BG layer to a null object, then track the null to the portal shot, so then you'll have both transforms. You can then adjust the keyframes from the drifting separately from the keyframes for the camera jitter applied to the null object.

--
Greg Niles
combustion Product Specialist
Discreet