The world of Horizon is vast and majestic, featuring lush landscapes crowned by seemingly endless skies. When the team at Guerrilla began creating this world, developers of various disciplines considered how to bring an immersive level of life to the world. For Guerrilla’s Atmospherics team, this meant populating the skies with lifelike clouds.
This work was evolved for Horizon Forbidden West. And now, in Burning Shores, Aloy will soar through more breathtaking, realistic skies than ever before.
The approach
“When we think of a horizon, we imagine vast expanses like the open ocean and how the clouds and the sun arc down to touch them at some immeasurable distance,” says Andrew Schneider, Principal FX Artist at Guerrilla. “Open-world games present developers with metaphorically similar challenges. How do we push the experience so that the player feels that they are in an environment that could be endless?”
It was one thing to ask the question but another to break it down into technical tasks.
In the early 2010s, feature film and animation VFX started using volumetric rendering to create clouds. For video games, this technique took too long to render with high-quality results at interactive framerates, but developers knew it held game-changing potential.
With innovations in hardware, this began to change. At the nexus of the PlayStation 4 in 2015, Andrew partnered with Nathan Vos, Principal Tech Programmer at Guerrilla. Together, they developed the highly efficient open-world volumetric cloud system that can be seen in Horizon Zero Dawn. The intricately detailed clouds framed Aloy’s world as a hopeful, beautiful one. It supported changes to the time of day and realistic animations, creating the sense of a fully living, breathing world.
This established the foundation the team would build upon for Horizon Forbidden West.
The evolution
In video games, clouds can help convey a mood. Along with the abundance of green, clear waters and cragged cliffs, the clouds of Horizon punctuate the world with emotion. To achieve this, they had to be more than white wisps far above the Aloy’s head; they needed movement, variety, and definition.
“We looked to artists who were part of the luminism movement for inspiration, like 19th-century painter Albert Bierstadt. These painters had mastered the interplay between clouds and the land beneath, using light and detail to create space, producing truly dramatic landscape paintings.
“To recreate this effect in 3D, we had to develop a way to model clouds. For Horizon Zero Dawn, we’d explored various methods for creating cloudscapes. Voxels are blocks that can build volumetric 3D clouds. We’d actually made a cloud simulator and experimented with rendering three-dimensional ‘voxel’ data in real time.”
“But technologically, it was too early for this,” Andrew recalls. “The hardware and software just weren’t at the right stage of development. So, we settled with modeling clouds in an efficient-to-render way that still yielded high-quality results, but with more modeling effort than simulation.”
The solution was to paint fixed layers of clouds rather than individual formations. But this process would need to be expanded to support the addition of flying mounts in Horizon F