Update: Nuke 8 fixed / added some of this functionality.

CameraTracker to RotoShape

The 3D Camera Tracker node in nuke is quite nice, but does have its limitations.¬†One of the cool things is that you can export individual tracking features as “Usertracks” and use those as a 2D screenspace track.¬†However you can only select tracks from 1 frame at a time and you can only export a maximum of 100 tracks in one single node. You cannot track single features manually and you cannot do object solving.

Well…. unless you use python =)


Extracting All FeatureTracks

I have created a script that returns a full list of tracking points from a CameraTracker node. This can for example be fed into a rotopaint node to do something like this:

Nuke CameraTracker to Rotoshapes from Hagbarth on Vimeo.


Here is some sample code that will let you export all FeatureTracks from a CameraTracker node:

; Function:             ExportCameraTrack(myNode):
; Description:          Extracts all 2D Tracking Featrures from a 3D CameraTracker node (not usertracks).
; Parameter(s):         myNode - A CameraTracker node containing tracking features
; Return:               Output - A list of points formated [ [[Frame,X,Y][...]] [[...][...]] ]
; Note(s):              N/A
def ExportCameraTrack(myNode):
    myKnob = myNode.knob("serializeKnob")
    myLines = myKnob.toScript()    
    DataItems = string.split(myLines, '\n')
    Output = []
    for index,line in enumerate(DataItems):
        tempSplit = string.split(line, ' ')
        if (len(tempSplit) > 4 and tempSplit[ len(tempSplit)-1] == "10") or (len(tempSplit) > 6 and  tempSplit[len(tempSplit)-1] == "10"): #Header
            #The first object always have 2 unknown ints, lets just fix it the easy way by offsetting by 2
            if len(tempSplit) > 6 and  tempSplit[6] == "10":
                offsetKey = 2
                offsetItem = 0
                offsetKey = 0
                offsetItem = 0
            #For some wierd reason the header is located at the first index after the first item. So we go one step down and look for the header data.
            itemHeader = string.split(myLines, '\n')[index+1]
            itemHeadersplit = string.split(itemHeader, ' ')
            itemHeader_UniqueID = itemHeadersplit[1]
            #So this one is rather wierd but after a certain ammount of items the structure will change again.
            if len(itemHeadersplit) == 3:
                itemHeader = string.split(myLines, '\n')[index+2]
                itemHeadersplit = string.split(itemHeader, ' ')
                offsetKey = 2
                offsetItem = 2
            itemHeader_FirstItem = itemHeadersplit[3+offsetItem]
            itemHeader_NumberOfKeys = itemHeadersplit[4+offsetKey]
            #Here we extract the individual XY coordinates
            PositionList =[]
            for x in range(2,int(itemHeader_NumberOfKeys)+1):
                PositionList.append([int(LastFrame)+(x-2),string.split(DataItems[index+x], ' ')[2]  ,string.split(DataItems[index+x], ' ')[3]])
        elif (len(tempSplit) > 8 and tempSplit[1] == "0" and tempSplit[2] == "1"):
            LastFrame = tempSplit[3]
        else:  #Content
    return Output

import string #This is used by the code. Include!

#Example 01:
#This code will extract all tracks from the camera tracker and display the first item.
Testnode = nuke.toNode("CameraTracker1") #change this to your tracker node!
Return = ExportCameraTrack(Testnode)
for item in Return[0]:
    print item

Remember if dealing with 1000+ features you need to bake keyframes and not use expressions as it will slow down the nuke script immensely.


Manual Single Feature Track

I did some additional tests with this, for example making the reverse of this script and giving me the option to add 2D tracks from a tracker node to the 3D Camera tracking node.


Object Solver

Now this is not related to the 2d tracking points but still a simple thing that should be included in the tracker.

Nuke Object Tracking