INSIDE LOOK AT "FREE BIRDS"
Q&A WITH WALTER BEHRNES, EFFECTS SUPERVISOR
He has also worked on such features as "The Ant Bully," "The Spy Next Door" and "The Spiderwick Chronicles," as well as the direct-to-DVD features "Open Season 2" and "Open Season 3."
From Relativity Media and Reel FX Animation Studios, "Free Birds" is the first theatrical full-length computer-animated film to be made at the award-winning Reel FX studios in Dallas, Texas.
"Free Birds" tells the story of two turkeys from opposite sides of the tracks who much put aside their differences and team up to travel back in time to change the course of history -- and get turkey off the Thanksgiving menu for good. The film opens nationwide on November 1st.
Q: What kind of effects can people look forward to seeing in "Free Birds."
A: The effects work in the film covers everything from fire and explosions to smoke, fog, dust, sparks and debris. In particular, the film leaned heavily on fire and fluid simulations, but the team had the most fun with the explosions, fireballs and flamethrowers. There is never a shortage of artists wanting to burn and blow stuff up when it comes to making a film!
Q: How do you approach a scene and decide what needs visual effects?
A: We evaluate the effects that are coming up in a shot and look closely at both the complexity and how much of each effect is needed. If it's an effect that will be used a lot throughout a scene or throughout the movie, we'll develop a tool system and a workflow that we're able to easily reproduce so that we can push out all those effects in a fair amount of time. We'll discuss the approach to each effect with a digital director and art director, figure out how we're going to create it, what's required technically and then move things forward from there.
Q: What was the most challenging effect to achieve in the film?
A: The first time the time pod (aka S.T.E.V.E.) is getting ready to be launched, we had to create a massive vortex around it. Just based on the amount of information that needed to render in that football field-sized spinning volumetric was daunting. It was about a five-month process to develop the right look and rhythm for that effect. The massive fog volume effect was not hard to create, but due to the sheer size of the effect, it was very tricky to get manageable render times without dropping desired attributes such as light scatter and motion blur." The team experimented with various render techniques such as point cloud look-ups to adjust brightness and shading within volumetrics, but ultimately ended up using lightning geometry as a light source while physically-based rendering the fog, which gave a nice scattering throughout the volume.
Q: I also noticed quite a bit of fire effects in the film, what was involved there?
A: In the film's third act, a huge fire overtakes the wild turkeys' lair, which is basically a series of tunnels. This was extremely challenging for the effects team to create. Population of the fires was achieved by pre-simulating multiple fire assets and developing a delayed load instancing placement and rendering tool set. The tool set allowed the artist to paint in pre-simulated fire as point data, visualize the placement in a proxy form, promote instanced points to geometry for hand placement and, if needed, push hand-manipulated assets data back into the instance point cloud for rendering, and finally render multiple passes and export animated proxy geometry to the lighting team.
Q: What types of tools were used to create the majority of the effects in the film?
A: The team primarily used Houdini software to generate effects and Nuke to create slap comps for compositing. Proprietary tool sets were created in Houdini and used to generate and animate the foliage on trees and bushes, and then to place the plant assets and populate vast amounts of grass. They also developed quite a few general tools to automate massive amounts of effects like torches, sparks and fuses.
Q: When audiences watch the movie, what do you hope they take away when they see your work?
A: We strive to create great effects, but we don't want them to stand out to the point that they take away from the story. Of course, I do want audiences to think 'Wow, that is a great explosion!,' but not necessarily on a conscious level. My hope is that they will be so immersed in the film that the effects never distract from the story that we wanted to tell.