Face Crack Tutorial: Part 1

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52,472

Updated:

Aug 12, 2005

Readership Level:

Advanced

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Shake Versions:

4.x, 2.x, 3.x

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irix, linux, mac, windows

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Language:

English

The Shake Comp:

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!



I 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 them.

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.



This 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.

7. 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.

8. 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 name.



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.

9. 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!)



10. 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:



The 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.
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