Motion capture revolutionized the film industry in the early 2000s when movies like The Lord of The Rings, Matrix or Avatar first hit the cinema screens. The motion tracking technology became so widely popular over the years that today, even Smartphone apps can be used to swap faces in a video or to completely replace them with the face of another person. Besides taking humorous photos with swaping face or head on your phone, you can now replace one's face with another in a video. However, people in video may move around, so you need to track the moving face to get a perfect swaping face video. Tracking the motion of an object in Adobe After Effects can be incredibly complicated when tracking complex motions, so in this article, we are going to take you through the basic steps of motion tracking that will enable you to replace faces in AE.
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Choose the video you’re going to use as a background and a photo of a face you’re going to use in that video before you launch AE, and then import the footage into the video editor. Keep in mind that simple slow movements are the easiest to track and that the amount of time you’re going to have to spend working on your project depends on how complex the movement in the shot is. After importing the footage and adding it a new composition, you should remove all parts of the video you don’t want to track by using the Split Layer tool and then go to the Tracker Panel.
After clicking on the Track Motion option you will be able to see a Bounding Box on the preview screen, and you can just reposition it to cover a face you’d like to replace. Go back to the Tracker Panel and click on the Analyze Forward or Analyze Backward buttons depending on the direction of the motion you’re trying to track. AE will then analyze the video and track the motion of the selected object. The Tracking Data will be displayed in the preview window after the video analysis is complete, and you can then go to the New submenu of the Layer menu, select the Null Object option and add it to the timeline. Click on the video to select it and then click on the Edit Target button in the Tracker Panel to make sure that the null object you created is selected. Hit the Apply button located directly below the Edit Target property in order to apply the X and Y dimensions to the tracking data. Place a photo or a video that contains the face you want to add to the background video on the timeline. Use the Pen Tool to draw a mask around the face, center the anchor point and position the face over the face you’re replacing. Pair the tracking data in the video with the overlaying image and the new face will follow the head of the person in the original video. You may need to adjust the tracking options manually if the head you added to the video doesn’t cover the face in the background completely.
Tracking Multiple Faces in Adobe After Effects?
Capturing motion of two or more objects requires you to open the Mocha AE plugin that is bundled with the Adobe After Effects. You must track each object separately and then copy the tracking data of the objects to the video on your timeline. You can then add a new face or any other object you want to the footage using the same tools you would use to add just one face.
Learning how to use the Mocha AE plugin requires practice and dedication because moving objects often have complex trajectories. The important part is to disable the motion tracking feature for one object while tracking another, since it may cause unwanted changes in the tracking data for the object you tracked first. Furthermore, if the trajectories of objects intersect you will have to track different portions of their movement separately, and even use manual tracking options in order to keep a new face over the face in the background video you’re covering.
How fast you’ll be able to replace a face in a video depends on the size of the video file and the computer’s processing power. Being patient and creating a mask that perfectly fits the face will make the effect more convincing. On the other hand, by just drawing a quick mask around the face you’d like to add to a video you may end up adding parts of the overlaying image that can completely ruin the effect. Do you use AE to replace faces in videos often? Leave a comment below and let us know.
Benjamin Arango is a writer and a lover of all things video.
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