retimestab.py

# Retime a tracked object to better fit a target curve
# Select two Transform nodes: the first with a jerky tracked curve, the
# second with a smooth target curve
# Group effort by Lewis Saunders, Unai Martínez Barredo, Erwan Leroy

# Make a function to calculate the distance between two points
def distance(a, b):
    return pow((a[0]-b[0])**2 + (a[1]-b[1])**2, 0.5)

# Find the closest point to p on the line ab
# Also returns the weight of that point along ab
# https://stackoverflow.com/questions/3120357/get-closest-point-to-a-line
def interp(a, b, p):
    if a == b:
        return None
    ap = (p[0]-a[0], p[1]-a[1])
    ab = (b[0]-a[0], b[1]-a[1])
    w = min(1, max(0, (ap[0]*ab[0] + ap[1]*ab[1]) / (ab[0]**2 + ab[1]**2)))
    return a[0]+ab[0]*w, a[1]+ab[1]*w, w

# Here we store the first node in your selection (the latest node you
# selected) as 'jerky', and the second one as 'smooth'.
smooth, jerky = nuke.selectedNodes()[:2]

# Find the first and last frame of your comp and the length in frames
root = nuke.Root()
first = int(root['first_frame'].value())
last = int(root['last_frame'].value())
clen = last - first + 1
crange = range(clen)

# We make two new empty list variables
jerkyc = []
smoothc = []

# Now for each frame (that we arbitrarily decided to call i) in the range, we
# look at the value of the curves, and add them to the lists defined above
for i in crange:
    j = jerky['translate'].valueAt(first + i)
    s = smooth['translate'].valueAt(first + i)
    jerkyc.append(j)
    smoothc.append(s)

# Create an oflow node
oflow = nuke.createNode('OFlow2', 'timing2 Frame')
# Set the frame knob animated
oflow['timingFrame2'].setAnimated()

# Go through each frame in the range again...
for i in crange:
    # Take the original list of the jerky values and sort them by
    # closeness to the value of the smooth curve, then keep the index of
    # the closest one
    closest = sorted(crange, key=lambda x: distance(jerkyc[x], smoothc[i]))[0]
    before = None
    after = None
    # If there are points on the jerky curve before or after the closest one,
    # check if there's a closer match on the lines connecting the closest point
    # to them
    if closest > 0:
        before = interp(jerkyc[closest], jerkyc[closest-1], smoothc[i])
    if closest < clen-1:
        after = interp(jerkyc[closest], jerkyc[closest+1], smoothc[i])
    # If there were points in both directions, figure out which one matched
    # best, and the offset from the closest frame
    if before != None and after != None:
        befored = distance(before, smoothc[i])
        afterd = distance(after, smoothc[i])
        offset = (-before[2], after[2])[(befored, afterd).index(min(befored, afterd))]
    elif before:
        offset = -before[2]
    else:
        offset = after[2]
    # Set the value of the timing curve on this frame
    oflow['timingFrame2'].setValueAt(first+closest+offset, first+i)