Definition September 2024 - Web

WATER SCENES VIRTUAL PRODUCTION

W ater simulation in CGI has advanced massively over the last 30 years, from James Cameron’s Titanic through to the amazing VFX in Avatar : The Way of Water . The technology has matured and rendering power is at the point where many effects can be run in real time. “The number one benefit of shooting on LED over green screen in a water- based environment is the reflections and refractions,” says Dan Hall, head of ICVFX at VP studio 80six. “We all know that no VP shoot will look correct without a good relationship between the VAD (virtual art department) and AD. When you have water in the foreground, you get an accurate representation of how it reacts to the light that’s emitted from the background. This helps sell the realism of what you are shooting.” Hall supervised a high-speed test that involved pouring drinks on a beach against an exotic beach background. “We were shooting at over 200fps when I noticed that the virtual sea elements were essentially stationary throughout the pouring. To add more movement to the sea, we did something that wouldn’t have been possible on location – we increased the speed of the waves. “To the eye, the waves appeared to be moving quickly, but on reviewing the shot they looked like they were rolling up the beach at only a slightly slower than normal speed while the drinks poured very slowly.” The way lighting from an LED volume penetrates practical fog on-set lends itself to underwater work. Craig Stiff, lead real-time artist and VAD operator at Dimension, explains: “Green screens cause green spill and would penetrate the fog, so practical fog would likely not be used and instead would be added in post-production. With LED volumes, the light is coming from visible structures which don’t have to be too out of focus. Reflections and out-of-focus edges are also accurate, meaning no painting out or rotoscoping/keying.” Having said that, it’s important to consider how the effect will be layered or composited as part of the final image.

For example, in survival thriller No Way Up , directed by Claudio Fäh, Dimension and DNEG 360 used SFX elements like fog and haze to give the impression of being deep under the ocean. This, combined with a virtual moon casting light through the fog, sold the idea of it being underwater. “On-set, we used two haze machines to add atmosphere to the practical set,” Stiff adds. “When used correctly, haze is a great tool for blending the LED wall with the practical set. We then composited VFX elements like ripples, bubbles and fluid simulations in post-production to blend the shots.” are caveats to the way you do things. When working with water, you need to take time to ensure everything has been set up correctly. For example, according to Hall, moiré patterns may become an issue, especially if you want to focus on a highly reflective object like water inside the volume.” “Any wire work (such as for PLAN THE DIVE, DIVE THE PLAN Like anything in virtual production, there swimming), has to be well planned and executed,” advises Stiff. “Hair and floating materials need to be considered because they won’t behave like they are underwater. Therefore, tight clothing, tied-back hair or head coverings are the best option, unless you can account for it in post-production.” PRACTICAL EFFECTS It is not only possible to augment video backgrounds with practical water effects but it’s encouraged for a more realistic final image as if you were on location.

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