With director Rupert Sanders at the helm, the film concept was taken back to the original darkness of the Brothers Grimm story. Will Cohen, Mill TV and Film's managing director/executive producer, explains: “The initial brief provided for creating the Mirror Man in SWATH by visual effects. Supervisor Cedric Nicholas-Troyan was asked to have the magic mirror on the wall melt/dissolve off the wall and form into a solid metallic/statue-like character in an elegant way. There was a process of discovery to go on in terms of how this would happen and what it would look like that led to five to six months of R&D. Cedric was keen to keep the audience wondering if Mirror Man was liquid or solid and to explore how he would move and what that would look like.”
According to Cohen, the work would split into three areas: emission from the mirror/wall, formation into Mirror Man and then his movement/performance. The director, Rupert Sanders, and Troyan had created a mood trailer to help get the film green-lit. They had a good reference for the design of Mirror Man as well as initial tests from the trailer for the Mirror emission and formation, Cohen added.
Troyan, who was then partnered on the film with VFX Supervisor Phil Brennan, suggested the group explore a live-action shoot before starting R&D on the computers to explore how different kinds of liquids and materials would react in reality. “We shot for a day with a Phantom camera at 1000 fps, upending tins of paint over upside-down dummies, heating up corn starch and playing with ink in water,” says Cohen.
Returning to the computers to emulate some of the tests, the team began emitting a controlled volume of liquid from the mirror and progressively morphing the emission into a solid shape. The results were not terribly satisfying, says Cohen, so they tried in parallel different approaches, such as meshed soft-body and, finally, cloth simulation, inspired by returning to the original teaser trailer where Troyan had literally stood up covered by a large sheet of gold lame.
Further tests were conducted to try and combine cloth and fluid. “Getting cloth simulations to behave like liquid was tricky to do without exploding the simulation,” notes Cohen. “We used Maya Cloth and wrote a lot of custom forces to control the cloth shape. Ultimately, the mirror emission was achieved by simulating cloth ribbon being pushed out of a hole, but a load of secondary effects had been done to deform, relax and smooth the cloth simulation in Side Effects’ Houdini.”
Playing with speed and direction helped to add weight as the emission hits the steps in the mirror chamber, adds Cohen. In helping production prep for the shoot, the group produced a lot of technical previs/design for the mirror on the wall shape and the witness camera design. “The plan was to use a reflective prop on set with a Red Epic camera inside to capture Charlize Theron's performance,” he adds.
Production provided the group with a 3D scan of the set, and they did a spheron survey. Cohen continues: “We then reconstructed the environment in 3D. The IBL and lights were separated so we could position candles or fire where needed. The Queen was then reflected in Mirror Man in 2D using UV normals and point position in world space so we could control the look. The real physical reflection would have made her almost invisible so these had to be cheated. Animating the formed Mirror Man was detailed, subtle and experimental because while we had to respect the phonetics of what he was saying, it is only when you see Mirror Man rendered and cut into the scene can you really tell what it looks like. Each shot then had a second layer of cloth simulation.”
One of the main challenges that Troyan and Brennan highlighted from the beginning was that Mirror Man was to be a large and fairly static full-CG character that would have nowhere to hide in a performance-based scene. “The Mirror Man is as much about the performance of Charlize Theron reflected in him as it is about him. We were very proud to take part in producing such an iconic and memorable sequence in the film,” notes Cohen.