G.I. Joe Gets VFX Retaliation
The art department created concept drawings of the satellite, and artists in London created a 3D model that was highly detailed, logically laid out and easily shared with other facilities. But because the detailed model looked so good, the filmmakers rewrote part of the movie's ending to add close-ups, and have it explode in space. This posed a challenge, so Beier envisioned an explosion in which flames would continue to expand and before eventually fading out. Digital artist Jeremy Hampton and the team created the effect in Houdini using a simulation that ripped the satellite apart in procedural way, based on DD's proprietary Drop system developed for 2012. The RBD simulation triggered and drove a pyroclastic blue fire explosion to finish off the effect.
Hampton and the team created the massive ICBM explosion, which, at 1 billion voxels, is the biggest simulation by far that the studio has ever created. The explosion was created based on reference footage of real MX Peacekeeper Missiles blowing up, where thousands of pieces of burning solid fuel leave distinctive smoke trails.
However, DD's most challenging shot lasts less than 10 seconds: the impersonation of the President by the Cobra henchman Zartan with the help of nanomites, the microscopic robots that form a living mask on his face, and reveal it in an unnerving scene where he appears to cut through his own skin to expose them.
Original plans for this shot were to achieve the transition between the President (Jonathan Pryce) and Zartan (Arnold Vosloo) photographically, by shooting both actors performing the same motion then blending them and adding the CG nanomites. When director Chu selected his desired performances, however, the two shots did not match, and the physical differences between the actors proved too disparate to bridge with a photographic approach.
Beier and the DD team then took the approach of creating CG models of each actor's head and using blend shapes, hand animation and the plate photography of the President to create the seamless transition from one to the other. The CG head models were created using the same geometry, point count and point order to enable the use of blend shapes to morph between the two models, using a 3D transition based on the topology of the face to control the movement of nanomites from one side to the other, which helped to even out the differences between the two head shapes. Because the shot is a full-face close-up, it was critical that the models maintained the features and characteristics of each actor, so in addition to using standard blend shapes, artists modeled and hand-animated facial expressions. Production VFX supervisor Madigan worked directly with DD's animators to art-direct specific facial movements. In the final shot, essentially the left side of the character's face (Zartan's likeness) is CG and the right side of his face (the President's likeness) is the plate photography, with the CG models of both faces blended between.
"In the end it looks mysterious and leaves you wanting more," remarks Beier.