War Horse required a wide range of VFX work from Framestore (with previs supplied by The Third Floor), ranging from simple paint cleanups to full digital stunt horses. From the outset, the overriding goal was to be stealthy and seamless, ensuring that the viewer had no idea they had ever touched a shot. There were approximately 210 shots in all.
"Early in previs development Steven had decided to avoid showing graphic shots of riders and horses being gunned down leaving the audience to make their own connection between the earlier mounted charging cavalry and the now eerie shots of riderless horses jumping over the German gun positions," explains Ben Morris, Framestore's VFX supervisor and the onset supervisor. "In order to safely shoot this action [when the British Cavalry is gunned down by the Germans], we worked with the stunt team and horse trainers, devising a system of horse lanes made from posts and tape that looked, to the free-running horses, like electrical fencing. While it proved a highly effective deterrent to horses straying off course, it required many weeks of complex frame-by-frame paint work for the five to six shots in the sequence led by Marc Rice and Rob Garner. Another obvious safety factor was that the machine guns could not be fired during shots including real horses, so we added practical smoke and muzzle flashes using 2D elements we shot at the end of the schedule."
For the tank chase of Joey, they decided to use a CG horse with such a tight schedule and after the real horses proved unreliable. "Starting from a synchronized, multi-camera photogrammetry session and flat lit texture shoot, Scott Eaton built our CG horse model and Michael Borhi painted a texture set based on a combination of the two 'hero' horse actors playing Joey," Morris explains. "The complex cannon harness and tack worn by Joey was also modeled from photographic reference. The horse was then rigged by Matthieu Goutte and Mauro Giacomazzo in preparation for animation in Maya . A number of in-house tools were used to setup the underlying skin/muscle dynamics. Long hair and short fur was groomed on the model by Rachel Williams and it was then setup for lighting and rendering by Stephan Putz using our in-house PRMan shader library and fur system. Stuart Ellis animated the two shots involving the tank jump and Carl Bianco created the secondary simulation rigs for Joey's harnesses and tack."
Behind German lines and under a barrage attack from British forces we rejoin Joey in one of the most complex VFX shots in the film."The shot became known as the Trench Jump for obvious reasons and involved three separate real horse plates and two sections of CG horse animation," Morris elaborates."Starting with the Third Floor previs of the entire Joey in No Man's Land sequence, we immediately recognized that the action in the first shot of a horse failing to jump a trench, crashing into the far wall, falling to the ground and getting up to run away would require our CG horse in some form or other.
"As Laurent Benhamo started animating the jumping, falling horse in Maya, we realized the second pan from explosion to falling sand bags would need retiming and re-racking to achieve the most believable horse action. At all times we updated the animation scene with refined body tracks and refined camera moves. By the time we got the animation to a state we wanted to show Steven, Mark Osbourne, our TD lighting on the shot, had prepared renders that could be comped into the plate. With little time to finesse the comp Julien put the shot together for our first review. When we played it to Steven and his editorial team in LA and heard winces and shouts of 'OUCH!!' down the phone, we had apparently hit the mark."
The final section of the sequence involves Joey running into a number of barbed wire barricades strung between Belgian gates. The wire gets increasingly tangled around Joey until he is finally catapulted to a stop when the broken gates he has been dragging collide with an obstacle.
"For all of these shots we captured reference of the horse action using our witness camera array," Morris adds. "We also dragged practical broken gates behind quad bikes as visual reference for the FX artists at Framestore to match to when they attached CG versions to the real horses.
"As horse safety was our highest priority on set, all barbwire used near the horses was breakaway plastic, and the horses were never allowed to have any lengths of wire trailing from their body.
"Ben Loch, Julian Hutchens, Noah Taylor and Daniel Fernandez were our barbed wire team for the end of the sequence. Working in Maya and Houdini, and using a combination of nCloth and our in-house fBounce dynamics engine, they wrapped complex trails of procedural barbed wire around the body tracked 3D model of Joey and then tuned the wires reaction to give just the right 'springiness' to match the real wire reference we shot on set. Before starting the final shots we got Kevin Jenkins' team to paint static concept frames for key shots with varying levels of wire tangled around Joey's body. Following a review with Steven, we started rigging the dynamic wires based on the approved designs. Kate Windibank and Ben Aickin lead the comp team bringing the shots of struggling Joey to completion using a mixture of 2D elements and CG soil, debris and dust passes."
Morris concludes that working with Spielberg and his team (particularly production designer Rick Carter) was like walking into a master class every day of the week. "The hardest, but ultimately most satisfying aspect of the use of digital effects in this film is that our work is hopefully invisible to the audience," he says. "We've just finished shooting Steven's next film, Lincoln, in Virginia, ready to start post in the New Year."
Bill Desowitz is former senior editor of AWN and editor of VFXWorld. He has a new blog, Immersed in Movies (www.billdesowitz.com ), and is currently writing a book about the evolution of James Bond from Connery to Craig, scheduled for publication in 2012, which is the 50th anniversary of the franchise.