2D Tracking - Nuke 101: Professional Compositing and Visual Effects - page 229

So how come, all of a sudden, you have animation in this property? You haven't
created any keyframes. Let's see...
9. Choose Edit Expression from CornerPin2D1's To1 Animation menu; this opens
the Expression panel ( FIGURE 5.26 ) .
Figure 5.26. The Expression panel.
The Expression panel shows a simple expression that points the current property
to “look” at the values of another property. It calls for the node (Tracker1) and
then the property itself (track1). The word parent is not a necessity and can be
dropped (if you want you can delete it and the dot after it). Also, there is no need
to specify X and Y for horizontal and vertical movement, because Nuke is smart
enoughtoworkthatoutitselfinthiscase.NukedoesthisbymatchingtheXvalue
atsourcetotheXvalueatdestinationandthendoingthesameforY.Youcanlink
any kind of property to any kind of property; it doesn't have to be positioned as
it is here. You can connect the Gain property of a Grade node to the Size prop-
erty of a Blur node. If the source destination had only one value or values that
were named differently than X and Y (like W and H, for example for Width and
Heightvalues),thenyouwouldhavetospecifyXandY(orwhateveritneededto
be—W, for example).