Epic films are usually not driven by visual effects, but are greatly supported by invisible effects that do not attract the viewer's attention. Gigantic historical sets are extremely expensive and only offer limited camera motion. CG sets are more flexible, offering more angles, more adjustments, etc. In the case of The Last Samurai starring Tom Cruise, the live action sword props couldn't be used in the close up shots, so Digital Dimension had to create CG swords and lances to allow greater realism. Benoit Girard, President of Digital Dimension walks us through the process.

Digital Dimension worked on 48 effects shots for The Last Samurai. Those shots included the integration of 3D swords and lances into live-action footage, crowd generation, and cosmetic effects such as a bleeding Tom Cruise. Discreet 3ds max was used extensively by Digital Dimension to comlplete the assignment.

Swordplay
Three major scenes in the movie featured the addition of a photorealistic 3D sword and lance into live-action footage. Two of the sequences involved Tom Cruise battling an army of warriors using a sword as his weapon, and one sequence involved a Samurai warrior throwing a lance. In all three sequences, the weapons had to be computer-generated involving textures, lighting and matching the weapons to Tom's hands. Because Tom's fighting choreography in those scenes is very fast and close to the camera, there was little chance a practical cheat would have worked.

“Tom was shot with a retracting prop sword that had to be painted and replaced with our CG sword“, explains Girard. “Tracking markers were placed on the soldiers to be stabbed so that we would have a reference in tracking the cg swords and spears. First we would track the 3D camera to match the movement of the live-action camera. There were so many soldiers moving through the frame that most of the camera tracking was done by hand. 3D tracking solutions have difficulty in scenes where markers or reference points are constantly being obscured. We would then matchmove the torso of the soldier to be stabbed. This enabled us to do animated linkages, driving the motion of the sword with the torso of the victim after he had been stabbed. This also facilitated accurate shadows and reflections. Finally we would matchmove Tom’s sword, replacing the stunt sword with a CG replica of the prop sword that was used by Tom in scenes that did not involve stabbing. One of the problems we faced in this process was that the sword handle would rotate unrealistically in the footage. It is very difficult for an actor to simulate the action (or inaction) of a sword being stuck in another actor’s body and reacting to that actor’s movement. This meant that sometimes we deviated from the live action sword to make the shot work. In the final shots, we occasionally replaced the whole sword and in some cases it was only the blade.“