Houdini flip simulation: Fabian Nowak breaks down the gravity scene in "Passengers"

May 2021 GridMarkets hosted Fabian Nowak, VES award winning Houdini artist, during which he discussed the breakdown of the gravity scene in "Passengers".

Houdini FLIP simulation at feature-film scale pushes both artists and technology to their limits. In this GridMarkets webinar, Fabian breaks down one of the most technically demanding water simulations ever brought to the screen: the zero-gravity pool sequence from Passengers.

From switching pipelines mid-production to delivering impossible shots under extreme deadlines, this session explores what it really takes to create believable water in a world without gravity.

The conversation dives into Houdini water workflows, production-level challenges, and the realities of learning new tools while shipping blockbuster visuals. Along the way, the webinar also touches on how cloud rendering solutions like GridMarkets make it possible for independent artists and studios alike to achieve film-level results without relying on massive in-house render farms.

Whether you’re working in Houdini, exploring large-scale simulations, or looking to understand how high-end VFX is built under pressure, this webinar offers practical insight, real production experience, and inspiration straight from the front lines of feature-film visual effects.

Watch the full webinar in YouTube

Behind the Scenes: Creating Realistic Zero-G Water Effects with Houdini | Space Station Inspiration

0:00: We had to create something never seen before.

0:01: We had to make all of that with Houdini, which, most of the artists at MPC at this time, never used, myself included.

0:10: So, first time opening Houdini, which, as you may know, is a pretty hardcore at the beginning.

0:15: And of course, we had to learn it on the fly, while at the same time we were trying to deliver some fairly complex shots.

0:21: And, so, as you know, there is nothing as efficient as learning on the battlefield.

0:27: It's probably for the best.

0:31: We had a quite limited budget movie, so nothing comparable to, big stuff like Lion King or Avengers.

0:41: but, despite being a low budget movie, it was very ambitious.

0:46: Therefore, the delay to deliver everything was relatively tight, and, we could not afford to have a large team of artists.

0:54: However, the amount of crazy requests was pretty insane.

1:01: For every department involved, it was actually quite a challenge in that regard, and all the effort was maximised as much as possible.

1:10: So, impossible task, new hardcore software to learn at the same time, limited time and resources, I think that was the right cocktail.

1:18: Pretty challenging show, but we do love challenge, otherwise we would be doing another job.

1:23: We start with the research and development, We looked at the storyboard and the first thing we thought was, how are we going to do that thing?

1:41: What could be the right approach to bring that sequence to life?

1:44: And, as usual, in order to demystify that, we start with a bit of R&D.

1:50: So, I'm gonna play those videos in loop, and mute them all.

1:59: We had to find some reference in order to know where we were going to, before starting the actual depth of the water.

2:07: Thanks to YouTube and thanks to NASA, we found some great footage of astronauts doing a bunch of tests of water. With water and zero gravity (zero-G) in the space station, with very small amount of water, of course, because they could not, you know, afford to risk to put some water everywhere in the space station.

2:25: I think it's full of electrical stuff over there.

2:29: We made some tests, in a very low gravity, which is the video on the very right side of the screen, which is not zero gravity, it's low gravity because it's in a parabolic flight.

2:41: But that means they could bring some bigger amount of water. laws of physics behind this behaviour that looks almost magical.

3:09: So we found out that when the gravity is removed, which is the main force driving the water behaviour on Earth, so when you remove the gravity, some other forces, which are usually negligible, are becoming all of a sudden the main forces in action.

3:24: Like the surface tension, for instance, which tends to make any body of water turn into a sphere.

3:31: And why that?

3:32: Well, because the spherical shape is the shape where the surface tension is the most evenly distributed.

3:38: There is no corner, there is no angle where the tension could peak, so, it's evenly distributed, so, that's kind of like the rest shape, if you will, the perfect shape.

3:49: If you let some water in G long enough and you don't disturb it, it will eventually turn into a perfect sphere.

3:57: But if you disturb it, I mean, if you had some external forces like having a momentum, for example, in FX you would say an initial velocity, or if you blow some air, to make some sort of wind, if you poke it with your finger, or if you throw an object at it to make a collision, like a tiny camera, like we can see there with the GoPro,

4:16: , or if you splash more water to it, or if you inject some air inside, etc.,

4:23: it will react accordingly, so it will make some surface waves, it will make some ripple, it will make some air bubbles inside that will inherit the motion of the swelling fluid inside the bubble of water.

4:36: Yet eventually it will try to maintain or to go back to a spherical shape.

4:41: , and we've also noticed, you could see that just a second ago on the left screen side, that the air bubble that could be trapped inside the water bubble will not escape.

4:56: They will stay trapped within that shield made by the surface tension.

5:00: So, that gives us a lot of hints for how, what we needed to see in that sequence to make it look sort of realistic, if we may say.

5:10: and from there, we started to do some development.