Exercise: Tracking in action
Click on the icon for a quick preview of the exercise and the final result.

Download an archive that contains the footage as well as the setups used in this exercise.
Put these files in your Flame system: for example under the /usr/tmp directory.

To learn how to load material into the Flame Library, see the exercise:
“Loading an archive”

Footage courtesy of: Interface Media Group / PBS
Images are subject to copyrights: please read the Disclaimer at the end of the tutorials.

We will work on a panning shot of the Westminster Bridge where we need to change the time on Big Ben. This is necessary because our shot has to be consecutive to other takes that were shot at different time of the day.

Start in Batch.
1. Change the duration to 20 frames.
2. Drag the Library node to the Batch schematic.
3. In the Library, select the clip “PBS_Bridge”.
4. Press Load.
5. Drag an Action node to the Batch schematic.
6. In the NodeSetup tab, set Auto Image ON.
7. Turn AutoKey OFF to prevent animating values over time.
8. Connect “PBS_Bridge” to the Action background tab.

1. Select the new media layer in the Action Media tab.
2. Click on Add media – From Lib.
3. Select the clip “New_time” in the Library and press Load.

To track an element on a moving background, use the tracker tool available in the Axis menu. In this case we will only track the position of the object, thus we will only use one tracker point.

1. Double-click the axis of the clock image.
2. Keep the default tracking options in the Axis tab:
Track
Rotation Off
Scale Off
3. Click on the Stabilizer button to access its menu.
4. At frame 1, position the tracker on a clean track point inside the clock.
Note: Pick the tracker by the middle to move it.
5. Keep the default settings and press Analyse.
If the tracking is not good, it is probably because the horizontal movement is too fast for the search area size. To fix this problem, increase the size of the Track box.
6. Go back to frame 1.
7. Change the Track Width to 30.
8. Press Analyse.
9. Scroll the clip to verify the result and RETURN to Action.

If there is rotation or scaling involved in the shot, if an object is getting closer in the shot for example, the Axis Track options need to be turned ON and two tracker points are necessary in the Stabilizer menu.

Once an axis is tracked, it contains the tracking data and it cannot be used anymore to move the object.
We will add a new axis that will be used to offset the object while the tracking will still be applied through the first axis.

1. Double-click the Axis node in the tool bin to add a new axis.
2. Disconnect the track axis and connect it to the offset axis, then connect the offset axis to the image.
Note: This connection scheme makes it easier to use the track axis as the parent of other objects if needed.
3. Rename the axes if you want.
4. Select the new offset axis.
5. Scale down and reposition the image to match the original clock position.
6. Rotate the Y axis slightly.

A track axis can be connected to other objects that require the same tracking movement.

To match the new image better with the backplate, we will color correct it in Action

1. In the Media tab, double-click the CC cell of the clock layer to access the Color Corrector.
2. Switch to CW.
3. Toggle to back view, press F2.
4. Zoom in and press Ref to sample the original clock color.
5. Return to result, press F4.
6. Bring the midtones track ball slightly towards the reference circle on the scope.
7. Select the ActionRes view in the view list.
8. Bring the contrast down by bring the Black slider down and the White slider up a little bit.
9. RETURN to Action.

The image looks crisp compared to the back; we will blur it.

1. In the Media tab, hold ALT to affect both sliders increase the Blur value to 20.
2. Add an Output node and process the result.

If you want to know more about the interface and the functionalities covered in this exercise, watch the following overview:

To continue practicing with the next exercise, click on the following link: