Tutorial: Kill the fake VFX expert with a katana


This tutorial shows how to realize a simple decapitation effect using After Effects and a green screen.
We realized a brief short film introducing the Tutorial to mask it as an interview.
This concept aims to entertain web viewers while passing informations on how to create the effect.

Set up the green screen and make sure that it’s evenly lit.
Shoot a scene with your executioner swinging the weapon.
Shoot a scene with your victim in front of the green screen while he makes a backward movement with his neck.
You can now replace the green with your executioner swinging the weapon.
To do this you need After Effects.
Use the keylght feature and adjust the parameters.
Make sure that both the timing and the color correction of the two clips match.
Change scale and position to make the reaction coherent with the swing.
Now you need to duplicate the victim layer, select the top layer, mask around his head , copy and paste the mask to the bottom layer but this time under “mask options” select “invert”. This way you’ll have the head in the top layer and the rest of the body in the bottom layer. Now duplicate the first layer another time, remove the mask and use it up until you want the head to fly off, when you’ll switch to the other two layers.
Set keyframes for scale, position and rotation, then, when you want to cut to the second layer you need to move the head up and rotate it a bit, then move it all the way out, scale it up a bit and rotate more. Feel free to play with this until you find the speed and movement that you’re happy with.
If your victim moves around a lot you’ll need to adjust the mask frame by frame to match his movement or use the tracking feature and then adjust it frame by frame.
Finally you need to place a photo to show the inside of the neck where it was cut off, mask around it and, again, make it follow the movements of the victim. You can make your photo a 3D object if you want to move it and rotate it along all the axis.
Then use a blood spurt effect, place it behind your expert layer and time it with the head cut off.
In the end you need to select all your victim layers and make a pre-composition out of them, then add a camera lens blur and set the radius accordingly to your needs.
The focus of the scene will be on your executioner and your effect will seem more real.

If you want to show your headless victim while he falls down you can do the same procedure once again.
This time you won’t need a green screen, just shoot the scene one time without any people and with the same camera and lights settings.
Make a mask around the head and track it.
Then cut and paste the mask on the layer with the empty scene.
Again make sure that the color corrections of the two scenes match.


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