Enormous moving cities posed all sorts of problems for creating realistic FX work. One of the essential visual moment cues was the chimney smoke generated by the cities themselves. To help manage these elements, the Weta Digital compositing team created a tool - a Nuke macro which contains all the Eddy simulation logic while exposing a few parameters to allow artistic control. Compositors could place the chimney smoke in 3D space, control the amount of smoke as well as the direction of the wind - all without having created a volumetric simulation before. This was a game-changing experience for the compositors: instead of spending time modifying existing elements from a 2D library to avoid repetition, they could create several iterations with this tool, allowing them to collide the simulation with the scene environment to produce variations and more interesting results.
Eddy was also used for ad-hoc simulations, adding extra layers of complexity to the images. This was helpful when it was not strictly necessary to draw on the resources of the FX dept and compositors could quickly add the new embellishments outside the original planned scope of the shot.
Due to the number of iterations required to develop the final look of the Medusa blast effect, Eddy was invaluable. Artists were able to work up different elements and quickly see how they would all come together. Many of the secondary and supporting effects for the blast were created and rendered in Eddy directly.
The majority of the shots in the Medusa core room used digital set extensions - which meant that we also had to extend the on-set dry ice effects, which had to match the live action plate seamlessly. We developed a tool for this effect, where one Nuke macro contained all the simulation parts. Compositors only had to place an axis locator in the scene and tweak the the density amount to match the plate. A second tool allowed them to procedurally light variations by sampling the plate and feeding it back into Eddy’s lighting system. The results were pretty amazing, and we were able to have a photorealistic dry ice element matching the plate in less than a day per shot.