Blackmagic Forum

Howdy --

I'm trying to figure out how to import a series of paths for a point tracker using the Fusion Python API (or if that's not feasible for some reason, Lua).

Unfortunately, if there's proper API documentation, I haven't found it yet -- all I'm seeing through the help menu is a directory with example code for very specific tasks. I've managed to get a handle on a manually-created Tracker object (albeit a roundabout way), but looking through its API using introspection (GetData, SetData, GetInput, SetInput...), there's nothing that's obviously suited to the task of "set position at frame N to X,Y", which is all I'm looking to do here.

Pointers -- at least, to the docs I should be reading?

No luck at finding official API documentation for Resolve 17, but there are fortunately some quite good 3rd-party docs, YouTube tutorials, etc.

I'd still be a lot happier to find official, maintained documentation; but to provide pointers to anyone else finding this, I ended up using code akin to the following to import 2d trackers exported from SynthEyes with "Export" => "Plain Text" => "Tracker 2-d Paths":

Code: Select all

if not 'tool' in locals():
   tool = comp.ActiveTool

def rescalePointFn(fromRange=(-1,+1), toRange=(0,1), fromRangeX=None, fromRangeY=None, toRangeX=None, toRangeY=None):
   fromRangeX = fromRangeX or fromRange
   fromRangeY = fromRangeY or fromRange
   toRangeX = toRangeX or toRange
   toRangeY = toRangeY or toRange

   fromScaleX = fromRangeX[1] - fromRangeX[0]
   fromOffX = fromRangeX[0]
   toScaleX = toRangeX[1] - toRangeX[0]
   toOffX = toRangeX[0]

   fromScaleY = fromRangeY[1] - fromRangeY[0]
   fromOffY = fromRangeY[0]
   toScaleY = toRangeY[1] - toRangeY[0]
   toOffY = toRangeY[0]

   def fn(x, y):
      # map from original range to (0,1)
      x += (0 - fromOffX)
      y += (0 - fromOffY)
      x *= (1 / fromScaleX)
      y *= (1 / fromScaleY)
      # map from (0,1) to target range
      x *= toScaleX
      y *= toScaleY
      x += toOffX
      y += toOffY
      return x, y
   return fn

def importPoints(filename, trackerName, destInput, startFrame=None, endFrame=None, ignoreValues=None, **args):
   rescaleFn = rescalePointFn(**args)
   try:
      comp.Lock()
      comp.StartUndo("Import points from file")
      with open(filename, 'rt') as f:
         for line in f:
            pieces = line.strip().split(' ')
            name = pieces[0]
            if trackerName != name:
               continue
            flags = int(pieces[4])
            if flags == 0:
               continue
            frame = int(pieces[1])
            if startFrame is not None and frame < startFrame:
               continue
            if endFrame is not None and frame > endFrame:
               continue
            x = float(pieces[2])
            y = float(pieces[3])
            if ignoreValues is not None and (x,y) == ignoreValues:
               continue
            x, y = rescaleFn(x, y)
            destInput[frame] = {1: x, 2: y, 3: 0}
      comp.EndUndo(True)
   finally:
      comp.Unlock()


Some notes:

• The mouseover status-bar text when looking at the inspector provides the names which can be used to look items up from the scripting interface (so the function can be passed `tool["Center"]`, f/e, if `Center` is shown in that bar).
• Note that, from Python, points can't be mutated in-place -- they need to be replaced with new objects.