Check out this Wētā FX-inspired Houdini FLIP fluid simulation
VFX artist David Krepelka has posted an interesting FLIP fluid simulation of water flowing over the human body inspired by the R&D work of legendary VFX company Wētā FX.
The demo, which Krepelka posted on LinkedIn earlier this week shows liquid flowing over a human arm and head, forming streaks and trails as it adheres to, then sheds from, the skin.
We think the approach used is based on the one set out in A Practical Guide to Thin Film and Drips Simulation, the 2019 paper by Wētā FX researchers Alexey Stomakhin, Andrew Moffat and Gary Boyle, which discusses the approach the studio took on action film Alita: Battle Angel.
In it, Wētā FX demonstrates that existing particle-in-cell (FLIP/APIC) solvers can be adapted to capture small-scale interactions between solids and water, down to fractions of a millimeter.
Implementing Wētā FX’s methodology inside Houdini
“I recently saw Wētā FX’s work [and] thought, ‘A little bit of stick-on collision, surface tension, and a couple of substeps, and you’ll get pretty close,” wrote Krepelka. “Damn, was I wrong.”
The eventual simulations are the result of Krepelka – whose day job is as a FX artist at VFX firm Accenture Song – digging deeper into the paper, and applying the methodology inside Houdini.
“Even though the sims are computationally pretty expensive, I really like the physical approach,” he says. “It just works!”
Kreplka is now working on test renders of the simulations, plus another shot of a character emerging from the water, so follow him on LinkedIn if you want to see them.
Read more of Wētā FX’s research papers in the Tech & Research section of its website
Watch demo videos of Weta FX’s in-house fluid simulation tools
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