Ever wonder what goes into some of the goriest horror film effects in films like Friday the 13th or Saw?
So did we, so we asked the team at Montreal-based special effects specialists Blood Brothers FX - led by Carlo Harrietha and Jean-Mathieu "Jib" Bérubé - how they might manage a head explosion, cutting an actor in half and doing your classic blood squirts.
How to explode a head
Here's why Blood Brothers know how to do head explosions - they had to make one possible for the low-budget indie horror Game of Death, directed by Sebastien Landry and Laurence Morais-Lagace.
Their hot tip for pulling off the effect is to actually combine as much practical as possible with some sleight of hand care of digital visual effects. The idea is to film a series of shots (called ‘plates') and then combine them in a compositing tool like After Effects.
Here's Blood Brothers' step-by-step, which involves shooting separate scenes with and without an actor, and with fake head pieces:
1. Film your first plate with your victim as if the head was blowing up and make sure your camera is locked. Bérubé adds, "Pimp up the camera resolution so you can add some movement in post-production."
2. Redo the exact scene without your victim. Have your practical effects crew do blood splatters from the exact point where the head blows up so you have blood and stuff actually interacting with the rest of your environment.
3. In post-production, select the shots you will be using and have a pre-comp (a rough composite) made by your visual effects team which will be used as reference for lighting and for positioning in your assets shoot.
4. Have a mold of your victim's head done in a material that will actually be destroyable. This is because, says Harrietha, "some silicone and other material that make-up effects guys use are very hard to blow up in a controllable way." Set up your fake head in front of a green screen in the same position and lighting as the original shoot. "Make sure the heads are filled with your favorite head matter," says Bérubé. "Let your pyro crew secure your set, set up their pyro and blow up the dummy heads."
5. Using a program like After Effects, take the shots of the original actor, the same scene without the actor but with the blood splatters, and the separate head explosion, and combine them. Boom! Head explosion.
Cutting an actor in half
It turns out Game of Death also had a scene in which an actor gets ripped in half. That's something that Harrietha says is "actually fairly simple to do old-school style. A couple of cuts at the right moment, some blood splatter, a pre-cut and dummy with some makeup, ground you can dig into and two people to create the illusion is all you need."
In this step-by-step, the Blood Brothers talk about how to cut someone in half with a katana:
1. Do your shot of the katana swing with both actors (killer and victim) but don't frame where the cut will happen. Have your effects team splatter and spray blood from that point to bloody up everything you want.
2. Do a close-up of a fake torso already cut in two sliding or falling apart. Put some blood lines with spray and have some falling fake guts and put blood slime and paste everywhere. "Make sure you ‘puppeteer' the bottom part of the torso towards the ground," notes Bérubé. "Stay on this shot long enough to hear the thud of the body hitting the ground."
3. Now it's time for the money shot. Set up your actor so you can bury his or her legs and body from the cut point down. Set up your double so you can bury the torso and head from the cut point up. Do not literally bury them, cover the hole with a breathable material and dressing over it to give the illusion. Make sure they can breathe by using material with holes in it and give them goggles and a dust mask.
4. At the point where the bodies disappear in the ground, cover it all up with fake blood, guts, paste and slime.
5. Shoot what you need to shoot. This technique requires no digital visual effects work at all so you can move the camera any way you like. For extra effect, says Harrietha, "have your actor's legs twitch at the same time as the arms, and have your actor spit out blood and say a last line."
Your classic blood hits are a staple of horror films. From knife slashes to bullet impacts, blood hits can involve both an effect to the body and a resulting blood spurt. The Blood Brothers (obviously) are pros at blood hits, and have two methods they follow; pneumatic and pyrotechnic.
Pneumatic blood hits consist of setting up a tube of blood and pushing high pressure air through the tube to evacuate the blood quickly. This can be done by either having your actors hooked up to an airline out of frame or with CO2 canisters on the actor with expensive solenoids.
According to Bérubé, the ‘pros' of pneumatic blood hits are a quick reset so long as the clothes don't get dirty, and no requirement for ear and body protection. However, he says, they can be slow to set up and the actor has to be hooked up to a line. You also have to pre-cut the clothes so that the hole will let out the blood, and doing multiple hits in one sequence can be complex.
Pyrotechnic hits literally involve adding a few small explosives on your actor - often called squibs. The idea here is that the explosives break through the clothing fabric and push out blood. But don't worry, there are in-built layers of protection for the actor.
"We must mention," says Harrietha, "that only qualified effects pyrotechnicians can do this technique, because if you do it wrong you will seriously injure someone. Remember that there is no reason whatsoever to put anyone in harm's way for a movie."
Pyro blood hits are faster and more precise than pneumatic hits and don't require pre-cut holes in fabric. If remote detonators are used, the actor can run and jump around freely, and multiple hits in a sequence are easier to pull off. But be warned, you'll need ear protection.
Be safe, not sorry
Remember, horror effects can be fun, but also dangerous if you don't follow the right procedures. Advanced effects need pros. Harrietha advises that you should "test your stuff before doing it on set, never do something to someone that you will or have not done to yourself, make sure that production leaves enough time so you can work on your effects shots properly and most importantly, be safe and have fun!"