Houdini was used for the core whip effect, generating dozens of different passes with varying degrees of amplitude, frequency and motion blur. The whips also generate sparks, smoke, molten drops of metal, grounding arcs and a visible trail of energy, for good measure. The whips have a grimy, industrial feel in keeping with real world metal cutting equipment -- and director Jon Favreau's aesthetic. As for damage, the whips scrape and gouge the track surface, slice through several cars and tear up Iron Man's armor. The car slices were achieved practically, but required CG enhancement with photoreal CG sparks, embers, molten-metal, smoke, dust and flying chunks of debris.

Of course, having the whips interact with Iron Man was a major challenge. This "Thermite" effect (created by Eugenie Von Tunzelmann) involved the whips wrapping around Iron Man and generating smoking, molten metal streaming from the superhero along with all the other whip vfx.

However, arguably the greatest creative and technical challenge for DNeg was the Iron Man suit-up. The suitcase posed a conceptual challenge for deployment and assembly of the armor, while the choreography of the close-quarters fight between Whiplash and Iron Man offered a different challenge.

To solve the suit deployment the team looked closely at the Mark III suit-up in the first movie but then departed from conventional wisdom by having the case start deploying while still on the floor so that when Stark lifts it to his chest, the armor is already partially formed. This also helped to balance the pacing of the suit-up so it wouldn't feel like the viewer was missing part of the action or that it was overly compressed as a cheat.

The final Mark V Iron Man model was comprised of thousands of individually modeled and textured components. The armor has a distinctive deep red color, originally conceived as a clear-coat finish combined with brushed metallic silver. The final look was more of a traditional Iron Man red finish coupled with chrome silver.

Motion capture clips were used to rapidly block out Iron Man's performance through the fight. This went through several animation passes to achieve the desired heroic style. Posing and movement were critical, and the DNeg team developed a collaborative relationship with the editing team in LA, changing animation, shot framings and timings, while also creating new CG shots and offering a mini-cut of the material.

Bill Desowitz is senior editor of AWN & VFXWorld.