An Affordable Army for Gods and Generals

"A huge serpent of blue and steel” is how one Civil War-erareporter described the phalanx of Union soldiers at the infamous Battleof Fredericksburg. When director Ronald Maxwell wanted to accuratelyrecreate that battle for Turner Pictures' Gods and Generals, heneeded to suggest the scope of a Union onslaught that was 122,000strong. The Gettysburg director had a large cast —including Robert Duvall as Confederate Gen. Robert E. Lee — butMaxwell didn't have that many soldiers. So visual effectsproducer Thomas G. Smith turned to Hollywood-based MetroLight Studiosto create an affordable army in 3D CGI.

The empty battlefield

“We'd assembled an army of thousands of Civil War reenactorswho came from every state. They showed up in accurate uniforms,carrying authentic weapons. But after the Sept. 11 terrorist attacks,many decided not to travel, and our army grew smaller,” Smithrecalls. “Large vistas showing thousands of troops became moredifficult to film. Fortunately because of digital effects, we were ableto put troops on battlefields that would have been more empty than theywere supposed to be.

“[During postproduction] Ron Maxwell realized the full extentof what visual effects could do, and he began looking at shots done bythe first unit as ‘plates’ for effects,” Smithcontinues. “Because these shots had not been intended as visualeffects plates, it was sometimes difficult to add newelements.”

The lines of soldiers began as animation-driven cubes to get an ideaof how they would move.

A wide shot of the Fredericksburg battlefield was a case in point.“It was almost like bringing a matte painting or a landscapephotograph to life,” says MetroLight visual effects supervisorJon Townley. “But this shot was the only ‘reveal’ ofhow big the Fredericksburg battle was. So we created double lines ofmarching soldiers, plus officers on horseback and wounded soldiersusing their rifles for crutches. We even added some soldiers crawlingaway from the line of action and thousands of corpses. The space inthis shot is so vast, we ended up creating over 17,000computer-generated soldiers.”

MetroLight CG supervisor Chris Ryan and Technical Director JerryWeil began the process by writing the MEL scripting tools that wouldallow them to apply 30 different variations of movement for CG soldiersanimated in Alias/Wavefront's Maya. “We had randomization ofspeed and directions — for walking, or running, or whatever eachguy is doing,” explains Ryan.

Ryan's first pass at animating the lines of soldiers, however,didn't resemble people at all. They were simply represented as cubesdriven by the animation, which provided Maxwell, Smith, and Townleywith a previsualization of how groups of soldiers could move. Once thechoreography of the action was approved, Ryan faced the task of turningthe cubes into plausible-looking troops.

Wireframe soldiers

Key concerns included making sure that the soldiers appeared to betouching the ground and that they were also moving in properperspective. “We built a three-dimensional terrain in Maya forthem to walk on because nothing in nature is flat,” Townleyexplains. “We'd also created over 3,000 dead soldiers that had tobe blended into the grass, which is another reason that we had tocreate the terrain. We laid this topography over the picture so that Icould judge the receding perspective lines. That way, the soldierswouldn't change from tiny to big too quickly as they marched forward,and the fallen soldiers would appear in proper scale.”

To accomplish this, Townley adds, “We had to figure out a[virtual] lens that matched the apparent parallax in the plate shot.Since the production crew hadn't thought this would become an effectsshot when they were shooting it, they didn't have camera information togive us.”

A closeup of the low-resolution soldiers.

While individual soldiers appeared small on screen, Townleynonetheless wanted to include details like shadows, which would groundthe soldiers in the scene, and glints of light on their bayonets.“These guys are relatively low resolution, but there are smalldeformations in their coats as they move, and they do have all theiraccessories, right down to the buttons on their uniforms,” Ryannotes.

“Because they're far enough away, we didn't need cumbersometexture mapping for every outfit,” observes Townley. “Ifyou could see these soldiers up close, they're relatively simple— what I consider ‘human brushstrokes’ in the sensethat there's enough detail for them to gesturally resemble photographedhuman beings. That was absolutely required for 17,000individuals.”

Final composite

The CGI was rendered with Pixar's RenderMan and composited into thebackground plate with Silicon Grail's Chalice (now owned by Apple).Compositing supervisor Jeremy Burns also incorporated live action smokeelements provided by Smith, as well as a matte painting of distantbuildings created by Toy Box West, Vancouver. The final composite alsocontained a retouched sky done at MetroLight with Adobe Photoshop.

What's significant to Townley about this assignment is itdemonstrates that these kinds of effects are becoming affordable formore and more films. “When a script says thousands of extras,there's now a way to achieve it. It's still not easy, but there's acertain point in epic filmmaking where you have to deliver an epicshot!”

Ronald Maxwell - Director
Thomas G. Smith, Justin Ritter - Visual Effects Producers

For MetroLight Studios:
Jon Townley - Visual Effects Supervisor
John Follmer - Head of Production
Matt Hullum - Line Producer
Christopher Ryan - CG Supervisor
Jeremy Burns - Compositing Supervisor
Jerry Weil - Technical Director