Making of Pompeii by Mr.X Inc
A breakdown of a RealFlow shot created by MrX for the film Pompeii.
“We had three months to create a hero water shot of Pompeii’s harbour as the Roman fleet arrives, from proof of concept to final delivery. This involved creating a large-scale water simulation for the ocean, which needed to interact with the harbour, cliff rocks, and the many Roman ships. We were given helicopter footage of ocean shores that were used as both a reference and a target quality for us to achieve. Our team consisted of six artists, including modelers, FX, lighting, and compositing artists.
The shot itself was massive: inside RealFlow the simulation measured 250 metres by 250 metres. At first I tested simulations at half the scale or smaller, but ultimately the real-world scale simulations had a superior look for this shot.The shot length was 136 frames, but because it needed to start as an active ocean—with foam swirling, waves crashing, and boat wakes—there was a lot of pre-roll, adding up to about 400 frames contributing to the final look.
The biggest challenge was achieving a nice balance of action. As an establishing shot it needed enough action to make the shot interesting, but not so much that it became distracting. It was during this process that I realised that a calm ocean can be as difficult to believably simulate as a chaotic water explosion.” – Eric Lacroix
“We used Hybrido2 for this shot because the water needed to have lot of interaction against the geometry of the harbor, rocks, and other features. With Hybrido I was able to simulatejust a tight section around the main parts of the scene, and then—using displacements—extend that main ocean pool sim into an entire endless ocean.
IDOCs were very useful for the foam and splash sims. There were a lot of foam particles to simulate: about 300 million! Thankfully this was a lot easier to sim since I could break it up into tiny sections and send it to our render farm using RealFlow Nodes.
We also used Graphs, particularly for the core body of water sim. I used the Surface Force Field graph in order to get the water to start moving in an ocean-like way during the pre-roll.In the graph the Ocean Statistical Spectrum Node was easy and fast to use in order to see how this would affect the Hybrido sims velocity. This way I was able to get things moving in a realistic and natural way.
RealFlow and Houdini
The lighting and render was done in Houdini. The great thing that RealFlow implemented was the use of alembic files: using them it was easy to output all of my sim data and get it imported into Houdini quickly and efficiently. Also, it gave the lighter and myself the ability to have many attributes on the particles, which were useful for correcting motion blur, normals, and UV mapping. I could also send Playblast renders to the farm for daily reviews to get the sims approved, then move on to the next step. Once the shader was in place and the displacements were dialed in we were then able to setup an ocean extension. Using grids with the core pool sim cut out, wethen applied the same displacement/water shader to give the effect of a vast ocean.”
//Source : http://www.cgmeetup.net/home/making-of-pompeii-by-mr-x-inc/