# Using the tracker functionalities¶

All tracking functionalities are gathered in the Tracker class. For now, only the tracker node can have a Tracker object. The Tracker object is auto-declared by Natron and can be accessed as an attribute of the tracker node:

app.Tracker1.tracker


The tracker object itself is a container for tracks. The Track class represent one marker as visible by the user on the viewer.

Tracks can be accessed via their script-name directly:

app.Tracker1.tracker.track1


The script-name of the tracks can be found in the settings panel of the Tracker node.

## Getting data out of the tracks:¶

In Natron, a track contains internally just parameters which can hold animated data just like regular parameters of the effect class

You can access the parameters directly with their script-name:

app.Tracker1.tracker.track1.centerPoint


Or you can use the getParam(paramScriptName) function:

app.Tracker1.tracker.track1.getParam("centerPoint")


Here is an example that retrieves all keyframes available on the center point for a given track:

myTrack = app.Tracker1.tracker.track1

keyframes = []

# get the number of keys for the X dimension only and try match the Y keyframes
nKeys = myTrack.centerPoint.getNumKeys(0)
for k in range(0,nKeys):

# getKeyTime returns a tuple with a boolean value indicating if it succeeded and
# the keyframe time

gotXKeyTuple = myTrack.centerPoint.getKeyTime(k, 0)
frame = gotXKeyTuple[1]

# Only consider keyframes which have an X and Y value
# If Y does not have a keyframe at this frame, ignore the keyframe
# getKeyIndex returns a value >=0 if there is a keyframe
yKeyIndex = myTrack.centerPoint.getKeyIndex(frame, 1)

if yKeyIndex == -1:
continue

# Note that even if the x curve or y curve didn't have a keyframe we
# could still call getValueAtTime but the value would be interpolated by
# Natron with surrounding keyframes, which is not what we want.

x = myTrack.centerPoint.getValueAtTime(frame, 0)
y = myTrack.centerPoint.getValueAtTime(frame, 1)

keyframes.append((x,y))

print keyframes


## Creating Tracks¶

To create a new track, use the createTrack() function made available by the Tracker class. You can then set values on parameters much like everything else in Natron.