Simulating sand and other FX, with Hybride

·October 12, 2022
·befores & afters

Go behind the scenes of the studio’s work on ‘The Book of Boba Fett.’

befores & afters recently caught up with the team at Hybride to discuss compositing on The Book of Boba Fett. Now we’re diving deep on the FX work the studio had to do for the series, including for creatures like the banthas and massiffs, and for the many different sand shots required.

Here’s what Head of FX at Hybride, Danny Levesque, had to say about the FX challenges on the show.

b&a: What were the overall responsibilities of FX at Hybride for Book of Boba Fett?

Danny Levesque: Our FX department delivered approximately 270 shots for the show. A lot of the action in The Book of Boba Fett takes place in the desert so we were responsible for generating a lot of CG dust for backgrounds, ships, speeder bikes as well as for different characters. Our team was also tasked with generating the sandstorm for the scene where the Tusken Raiders find Boba Fett in the opening episode.

We also had to get friendly with the Tusken Raiders’ ‘pets’, the banthas and massiffs. We had to do a lot of different tests to figure out how we could get the sand to interact properly with the beasts’ paws whether they were walking, sitting, or running.

We also textured the massifs’ very peculiar skin. Our team spent a lot of time figuring out how the massifs would deform in CFX. Their skin resembles very thick leather, so we needed to find a good approach to enhance certain details and behaviors at the right spot and at the right moment.

b&a: How did Hybride tackle and fur and cloth sims for creatures and characters?

Danny Levesque: For the banthas, we started with the rig and ran a pass of CFX to add belly jiggles and fix any issues or problems in the mesh. This was crucial to produce a smooth and perfect deformation without intersecting geometry.

For the fur, we had to perfectly match the groom provided by another vendor, so the main challenge was matching something that was already existent. We generated the guides for the CFX department from the final groom and that is what they used perform simulations using Vellum.

Since the groom was comprised of millions and millions of hairs, we couldn’t brute force it into sim. We tested it, but the sim times weren’t very encouraging, so we came up with an in-house solution which helped us to perfectly capture and wrap the final groom onto the simulated guides. This gave us the advantage of very fast turnaround times to adjust the sim with different settings.

For most of the characters that were not heroes, such as the Tusken Raiders on speeder bikes in the background, for example, we used a combination of simple layered noises to fake the wind catching in the cloth of their cloaks. Whenever we couldn’t do it with simple noises, we turned to the Vellum solver.

b&a: How did you tackle sand FX or sims for the show?

Danny Levesque: Since we previously had the opportunity to work on shows where a lot of the action takes place in the desert, we were already in familiar territory! With every project, we continue to improve and refine an already well-established internal workflow.

For each interaction that takes place in the sand, we relied on the amazing grain solver in Houdini. We developed a set of Houdini Digital Assets (hda) around what we call ‘ground interaction.’ As the name suggests, the hdas were created to deal with any type of character interacting with the ground and each one of them played a very specific role. They automatically took care of the character/ground prepping, simulating, uprez’ing and packaging the caches.

When chained up, we basically only had to change the inputs (characters and ground) to produce a new shot. The key to this was to obtain a solid preset (which we established at the beginning of the show) to define the type of sand we were looking for. After that, it took only a few minutes to flood the farm!

Finally, we performed a first ‘blind take’ and addressed specific notes if needed. Using our FX Qc Render tool, we rendered a technical pass to get the motion and size on the sand that had previously been approved by the supervisor and from there, our brilliant lighting team took it up to the final stage.

b&a: Were there any particular tools of choice used inside the FX department (including any particular aspects of Houdini utilized this time around)?

Danny Levesque: The Houdini grain solver helped us achieve the look and feel of a character walking around or running in the sand. It’s fast, robust and it gave us an incredible amount of control to fine tune every aspect of our sims.

For the sandstorm, the dust elements were generated into hero shots using Houdini’s Pyro. For all the non-hero shots, we worked with the comp team and fed them with generic VDBs. We figured it would be much quicker to adjust the feel of a shot directly in Nuke using Eddy to render the volumes. That way, we were able to bypass the lighting completely, which saved us a considerable amount of volume rendering.

Also, one of the main challenges in FX is data management. We always create too many caches and produce tons of terabytes! I think that over the years, Hybride has succeeded in giving its artists the tools to create and manage their caches. It’s important to be organized while using a proper naming convention.

It’s also crucial to know what’s good and what’s not when you’re generating a lot of versions. That’s why we’ve completely wrapped the regular file cache into an hda to quickly read/write our caches. It also allows us to save all the necessary metadata (ex: comments, Houdini version, .hip used to generate the cache…) within each version. Artists shouldn’t have to worry about where to save their caches: we need them to focus on creating the best effects as possible!

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