All images courtesy of Lionsgate.

Leave it to writer-producer Joss Whedon to team up with director Drew Goddard for Cabin in the Woods and create a meta-horror film that not only delivers the chills but also manages to be very funny. But the movie posed an interesting challenge for VFX supervisor Todd Shifflett of Rhythm & Hues, who's not a horror fan. Thus, Shifflett says working on Cabin was an eye opening experience, not the least of which because it entailed some interesting design choices for the gallery of ghoulish creatures. "The more gruesome and bloody we could make it, the happier they were," he relates. "The crazier the monsters, the more they liked it."

As with most visual effects projects, the biggest challenge is the time you're given. "It seems that more and more we're given less and less for each project," Shifflett suggests. "They also went back and forth about 3-D conversion and then dropped it. Personally, I'm not a big fan of 3-D. We spoke to a lot of companies. They tested and I'm glad they decided not to do a 3-D release."

They didn't reference any movies in particular, which is ironic because it's such a self-reflexive horror movie. But there were a couple of things that they dreamed up; namely, the dragon/bat. "They said, 'Come up with that.' So we came up with some design sketches and bounced it off of them."

The dragon/bat is about six-feet tall with a giant wingspan. They obviously had wide latitude with the dragon part, referencing comics and providing a Neil Gaiman-like influence overall. But with the bat part they did a lot of research."They [particularly] liked the blood around the mouth and the way the jaw opens," Shifflett recalls. But there were many considerations, including the texture of the body and the scales and fur.

"It's going to have to fly down hallways or scream at the camera, but does it have to grab something with its talons and eat it?" Shifflett continues. "We had to cover all the bases."

Another difficult creature was a ghoulish apparition. The filmmakers didn't want it to look like an X-Men superhero but they wanted it to be scary. "It was a combination of a fluid dynamic system mixed with some three-dimensional elements of bones and skeletal features that would dissolve into this fluid, atmosphere effect," he recounts.

Destroying the cabin using a model provided a more conventional opportunity.

Meanwhile, among the more than 300 VFX shots for R&H were half a dozen other hero creatures to be animated along with plate and green screen work with live actors in gruesome costume and makeup. Among them were giant spiders and snakes, which were stitched together like Frankenstein, repurposing old animated creatures and enlarging them or adding heads.

There's a giant snake that has to go into a small hallway and it's covered in blood. "We filmed in a space in Vancouver, where we weren't allowed to throw things around in their hallways," the VFX supervisor says. "And so it came to us later on to have to cover the walls with blood and debris and try and fill the place with smoke. It was an interesting set augmentation problem."

For the cabin itself, R&H built a CG model purely for the destruction scene: "We modeled enough detail to see boards and individual pieces breaking apart. You get a sense of the architecture falling apart."

There's a monster rampage called "The Costco of Death," which posed two significant challenges. It not only required elaborate compositing but also demanded a tricky engineering feat since the elevator is actually comprised of a thousand cube-like structures that slide around everywhere simultaneously like a Jenga game.