Let your actors do their own stunts (in After Effects) in your next project with this action-packed car chase video tutorial.
Top image via Troublemaker Studios.
In this latest After Effects/practical effects tutorial from Cinecom.net, we learn how to convincingly pull off the classic “actor on top of moving car” stunt that you’ve seen in almost every action movie since you were a kid. The effect is a perfect combination of practical camera movements, green screening, and motion tracking. This channel has really hit its stride and is currently producing some of its best content yet, so go on over and subscribe for more filmmaking tips and tricks.
How It’s Done
All images via Cinecom.net
First things first, mark some trackers on the window that your subject will crawl out of. This will be what After Effects uses to track the car’s movement. You can use masking tape for this. To make your actor’s hair blow in the wind, just use a garden leaf blower.
Then, to make sure you have the car in the same place in the shot, use a marker to outline the car on top of the monitor so that when you shoot the green screen coverage, the car is in the same place. This is a brilliant way to make your life a whole lot easier in post-production.
With the new driving shot composition opened, open the tracker window, then select “Track Motion,” then enable the tracking of the Position, Rotation, and Scale. Then you’ll see two tracking points come up on your shot — this lets you position them on the tape trackers you’ve placed on your window. You only need two for this example because After Effects can calculate a change in position or rotation in the shot. Once you’ve done this, hit the “Track Forward” or “Play” button, and then wait to see if the track worked.
Then create a new Null Object Layer. From here, go back to the Tracker window and hit “Edit Target,” then select Null 1, and then hit “Apply.” Then add your green screen shot on top in the composition. Take the Pen tool, and draw a mask around the window and a portion of the green screen. Next, you’ll apply the Keylight effect to that green screen layer, which will let you remove all the green. Then click on the green screen clip again, hit T on the keyboard, and change the Opacity to 50%. Reposition the clip so that it matches the driving shot, then change the Opacity of the green screen clip back to 100%.
To make sure the clip stays in position, take the Parent pick whip and drag it to the Null object (which holds the tracking data). You’ll see now that the two clips are seamlessly connected and the sequence works! Throw on whatever grade you want, include some lens flares from our Lucent Warm pack, and you’re good to go!
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