1. File-In the footage. faceCrack_original.jpg.
Play through a few times and check the position and nature of the
markers. You will see that at a certain frame they are obscured by his
left hand and are not revealed after that. So we will only need to
repair the plate up until that point.
2. Shift+Click to branch a
Transform=> Stabilize node off this file-in. We will use the tracker
to lock a roto shape to each of these markers which will act as our
matte to allow us to KeyMix the slipped versions of the plate. (if you
are using shake v3 or later you can just RMB on a RotoShape and select
�add to tracker� thereby eliminating the need for some steps here) You
could also use a MatchMove node but lets stick with stabilize for now!
won�t explain the difference between the pattern region and search
region etc, the manual is there for that. But I will mention that I
chose to use a �stabilize� so I can detach these nodes and hook the
roto shapes straight into them and the use their transform to animate
When Tracking it is important to turn �on� the limit
processing attribute, so that shake will set a DOD at the edge of the
search region, dramatically speeding up the whole process. Once again
not so vital in this example but at 4k�..
3. Go to frame 1 and
place the tracker over a one of the black markers. Making sure that the
cross is over the centre of the marker.
If we look at the
default settings for our tracker, we can see that we are tracking the
luminance of the image. Since the skin is nice and bright, and the
marker is black, this is a good start. The reference tolerance will not
need to be tweaked for this shot. Make sure that the reference
behaviour remains set to : start frame. As the markers appearance will
not change in the shot.
4. Now hit the track forward button. If
you loose the marker in the course of the track, pressing [Backspace]
will eliminate any �bad keys� and progressively move the shot backward.
Pick the last good frame and hit the �reset track search area� button.
is a fairly easy shot to track so you should have minimal problems,
until you reach the frame where the hand obscures the markers. There is
no need to track the dots after this stage any way so you can
[Backspace] away any odd keys and move on.
5. Go to frame 1 of
the sequence, create a RotoShape node, load the plate into the viewer
and make a four point shape over the black dot you have just tracked.
Make the shape slightly bigger than the marker itself. This is
important as we will feather this shape later.
6. Extract the
stabilize node (you can use the [e] key for this) and place the
RotoShape in its input connection Append an over node to this stabilize
and place the plate in the background input. Like so :
This will allow us to check out the accuracy of the track with something other than the tracker box itself.
Load the parameters of the Stabilize node into the parameters tab and
set applyTransform to active and set inverseTransform to match.
This will transfer the tracked data to the RotoShape.
Scrub through the sequence and check the accuracy and stability of your
matched RotoShape. You may notice some frames where the track is a
little noisey or inaccurate. To fix this. Load the parameters of the
stabilize node and scroll down to the bottom of the tab. Expand the
parameters of track One and load the trackX and trackY parameters into
the curve editor by ticking the clock button next to the parameters
This is our tracking data. If you zoom on this graph you
will see a couple of spikes in the track, probably caused by
compression on the plate or just the default settings of the tracker.
Select both curves, making sure to grab all points and smooth out the
curves using the default setting. (If you are using shake 3.x or higher
your curve editor may have buttons in different places!)
Once this is done you should have a smoother track. Delete the over
node and create a layer=> KeyMix node. Append a move2d node to the
footage and connect the footage to the foreground input of the KeyMix,
the move2d to the background input of the KeyMix and the stabilize node
to the matte input. Also place a blur node in-between the stabilize
node and the KeyMix node. Your tree should look like this:
Move2d will be used to slip the plate and the RotoShape will act as an
alpha channel cutting out the foreground input and revealing the BG.