Motion Tracking in VFX

 

What is Tracking in VFX ?

Tracking is the process in which we locate the changes in position of several points in our video footages then this tracking data can be used to either stabilize the video, solve the camera or to link another video to this.

Well this was just a defination, now let’s take a detail look of Tracking in VFX , what are different types of tracking , what’s the use of tracking and many more.

What are different types of Tracking in VFX ?

In VFX there are 3 types of tracking which are used for different purposes

1. Motion Tracking

2. Camera Tracking

3.Object Tracking

Let’s have a look at each of them and understand better where , why and how these types if Tracking in VFX are used.

What is Motion Tracking ?

As the name suggest, Motion Tracking means to tracking the motion of any object or a point.

Let’s see it through an example.

In the image shown we have a square box with a plus sign . This is the Tracker that will track the motion . Now suppose the ball moves from its position in video footage then in the tracking process the tracker will track the motion of this ball . Hence now we have the data of how the ball performed its motion and if now we take another video and link it to data then it will have the same motion as the ball is having . This is how Motion Tracking works.

Where is Motion Tracking used ?

Motion Tracking is used when we have to link another video in compositing to the motion of another video . If it does not sound good , then let’s understand through an example. Suppose we had a video of Mountains with a clear sky and the camera is moving or panning. Now we supposed to replace the sky and add a clouded sky . So we key out the clear blue sky and added a clouded sky behind it. But since the camera is in motion the sky behind we just added we not have any motion and this will look ugly that the mountains are moving and clouds are static. Hence we track the motion of Mountains and add it to sky. Now both sky and mountains move together and hence Tracking in VFX is most important.

How to do Motion Tracking in Nuke ?

 Point Tracking in Nuke

There are 3 types of Point Tracking Options in Foundry Nuke . These are -

1. Single point tracking

2.Two point tracking

3. Four point tracking

Single point tracking : If the video footage has only movement in one axis then the single point tracker is used. If there is no scale , no rotation etc.

Two point tracking : If the video has movement in one axis and also rotation then 2 point tracker is used. Note that two point tracker can only track the motion in z direction.

Four point tracking : If the video has movement , as well as rotation, scale then four point tracker is used.

How to do Point Tracking in Nuke (Step by Step ):

1. Using search option take a Tracker node and attach beneath the footage to be tracked.

 2. From the properties panel click on add track

 3. Now place the tracker marker on the desired location to be tracker.

 4. To Track forward click on the play button icon show below.

 5. After the tracking is complete then from properties panel in export select Transform (Match-Move) and press create

 6.Now you get the Transform Matchmove node with all the tracking data in it.

 7. Now the final step , using read note bring your footage that is to be composited. Then use a merge node to assign the background and forground. Then attach the tracking matchmove node as shown below.