'Biomorph', a promo spot for Nike's Flyknit tech, is nominated this year for a VES Award for both Outstanding Visual Effects in a Commercial and Outstanding FX and Simulation Animation in a Commercial or Broadcast Program. We talk to Digital Domain visual effects supervisor Aladino Debert about the piece, which was directed by Mothership's David Rosenbaum.

Watch a breakdown of the spot.

The spot highlights how the new show technology acts as a seamless fit to its wearer - with DD creating both an anatomical view of a human foot and the shoe as it 'knits' together. To get a feel for the manufacturing process, DD toured Nike's Portland facility and saw the shoe being made on industrial knitting machines. The final spot conveys the formation of a runner's foot and then the knitting of the shoe around it.

A real foot was filmed on a stage with a Phantom camera as reference and to form part of the transitions from the anatomical and shoe shots. "There was something particular about the way the runner was supposed to run, as opposed to the way most people run," says Debert. "Usually people put their heel first, but it's the worst way you can run. Professional runners put the ball of the foot first, which makes sense because it has a lot of fat around and is cushy and allows your calf to function as a shock absorber, something you cannot do if you land on your heel."

A key frame became the underside view of the foot landing in which muscles, nervous system, fat and sinewy material inside begin to form into skin - this was filmed as the runner takes a step on top of a plexiglass platform. "Then we did a roto-animation - we animated our IK system with the bones, muscles and veins to match the animation of the foot. Then we created a bunch of revealing masks to combine in comp."

"We had to walk a very line between realism and creepiness and art direction," adds Debert. "We wanted to make sure on screen it would remind you of an inside of a foot but without going creepy." That meant DD removed certain things from the foot, and added in instead translucency, making sure the light from behind would shine through. Sub-surface scattering was something artists spent a great deal of time perfecting for the skin.

For the knitting part of the spot, it was important to portray how the shoe was pieced together with almost no seams and far less pieces than a traditional jogger. However, the threading was perhaps one of DD's most challenging aspects since the animated growth was shown extremely close to camera. "We had three effects artists working solely figuring out a way to make the knitting work," recalls Debert. "We worked on three different approaches before it looked right and could actually render. One approach was taking 50 hours a frame to render!"

See a breakdown of the knitting sequence.

DD tried a hair approach first, but found that getting the right scale and having it art directable was tricky. A shader solution also did not provide enough fine detail. "The added complexity was that every fiber you saw animating was made out of 50 individual fibers themselves," says Debert. "We had to find a way to animate each of the clumps but also a way to essentially replace the single master fibers with a clump of fibers to look like the real thing."

The approach that worked involved using spline curves animated with a particular type of deformation that would provide the necessary rotation. Particles were generated along a set path and the curves would follow and interact with its neighbor, and a further system provided uneven edges. "Once we had the sim done and liked the speed of the curves we would then replace it with the clumps - the clumpy fibers follow the master curves and generate their own geometry to make them look like they were made out of fibers," explains Debert.

The result is a spot that communicates that Nike both understands the way human feet work, and excels at manufacturing a shoe with the most comfortable fit. Says Debert: "The message they wanted to portray was the shoe was put together in a way that it feels almost like you're running on just your feet."

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