Space Sweepers came to us with quite a challenge - build a huge space station, smash it into the Earth, and follow the events down to a closeup of a city getting destroyed by the blast. All that grand scale with a short schedule asked for some innovative problem solving. So we went to work, starting with world building. The movie called for a 1000km sized space station in the made from compacted garbage towers. The North Pole is occupied by a central city, with radially spreading streets along which the towers are placed. Building in Houdini, we produced a bunch of variations of the garbage towers procedurally - this approach is serving us very well in world building. With procedural assets, you can generate any amount of variations you need, and edit them easily as they automatically regenerate. The streets are guided by the mesh topology of the sphere, carving it up in sectors that we populated with the garbage towers. Attributes on the surface and randoms seeded by the pieces of geometry allowed for deep variation in the shaders of the assets. The city at the pole was an amalgamation of predesigned towers. FX wise, we knew that we needed a huge number of events, so we did a similar thing - used Houdini’s proceduralism to generate several variants of all the events - explosions, smoke trails, debris streams - and populated the surface with them. We rendered in V-Ray for Houdini, and it’s the first time we had NINE THOUSAND explosions inside the frame! To efficiently recreate the Earth, we went for a combination of the highest resolution photos we can find, and extra cloud layers - both from aerial photography plates, and simulations in Houdini. For the shots where the huge smoke wave travels across the surface of the planet, resolution and efficiency were most important. Same solution - design a smoke front first, then bake out a bunch of variations, and place them along the arc, to get the advancing smoke wave with a much bigger resolution than could be simulated at once. Explosion at the background was more traditional - mighty Pyro ball at the horizon, adorned with some streaks and debris. Getting to the city - again aiming to be speedy, we put some kitbash buildings in a library, and tried a procedural build. Turns out cities are complex(duh) and only the real ones look correct. So we picked up a real city, ingested the OSM data into Houdini, and placed our library buildings on the places of the real ones, picking an appropriate using the map info - height, house or tower, etc. The lines for roads were the starting point for procedural roadworks, and the parks were populated with vegetation. In the last shot we had to destroy the closeup buildings quickly. Picking the same library towers, we destroyed proxy geometry derived from them, and then transferred the animation. This is a very robust process, saves all the time that would otherwise go into dealing with geometry not designed for destruction. The pyro was again sectioned and simulated in parallel for more performance and maximising resolution. Glad to see Space Sweepers become the underdog success it deserves! It’s flamboyant style and technical challenges lead us up the ladder, too :) Hristo Velev, VFX supervisor at Bottleship
