Liquid Simulation Series: Mountain Dew part 1

The Smoke & Mirrors CG team has been hard at work honing their fluid simulation skills in the past few weeks, first with a complex spot for Mountain Dew India featuring a gushing dam and then with a beautifully smooth piece for Hornitos Tequila.  Simulating the frenetic surge of a large scale dam in RealFlow for Mountain Dew was a welcome challenge for the CG team, and the research they conducted to complete Mountain Dew helped them to quickly and easily nail the simulations to finish the Hornitos piece.

There were two main challenges to simulating the dam flow:  scale and resolution; Scale was the largest hurdle for the team to overcome. In order for the liquid to feel massive, an accurate scale needed to be established early on for the particle simulations. Had the real-world scale been ignored, the liquid would have felt like it was operating in miniature.  Working at the scale of a dam, however, created other challenges in terms of render time and resolution.

To accomplish realism at such a scale, the fluid simulation actually required a conglomeration of several smaller simulations: one to create the main, massive flow of water down the dam and then several others to simulate the various splashes that occurred in the waters’ journey down the slope.

Ironing out the main flow first, the team simulated this surge without the other splashing elements using a grid domain.  This helped to contain this specific flow and allowed for faster and more predictable simulation. 

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The next hurdle the team encountered was resolution, aka how dense could they simulate the particles and still finish the job on schedule. Since it was concluded that they would be using mostly particle shading for the foamy whitewater, the particle density needed to be extremely high - much higher than the traditional mesh shading common to smaller liquid jobs. Some of the scenes clocked in at upwards of 25 million particles.  For purposes of testing however, simulations were run at 1/50 of the final resolution that they were to be rendered.   At this scale the team could get a clear idea of the physical properties of the fluid that needed tweaking to perfect the simulation without having to deal with the heavy renders.

Having tackled the main flow of water down the dam, the team then dove into R&D for the various splash simulations.  This was a complex process that required work at a very high resolution....check this space tomorrow to see how the team achieved this!