The world of Horizon is vast and majestic, with lush landscapes crowned by seemingly endless skies. When the Guerrilla team started creating this world, developers from various disciplines thought about how to bring an immersive level of life to the world. For Guerrilla’s Atmospherics team, that meant populating the sky with realistic clouds.
This work was developed for Horizon Forbidden West. And now, in Burning Shores, Aloy will soar through more realistic and breathtaking skies than ever before.
The approach
“When we think of a horizon, we imagine vast expanses like the open ocean and how clouds and the sun set to touch them from an immeasurable distance,” says Andrew Schneider, Senior FX Artist at Guerrilla. “Open-world games present metaphorically similar challenges to developers. How do you push the experience so that the player feels in an environment that could be endless?
It was one thing to ask the question but quite another to break it down into technical tasks.
In the early 2010s, feature film and animation visual effects began using volumetric rendering to create clouds. For video games, this technique took too long to render with high-quality results at interactive frame rates, but developers knew it had game-changing potential.
With hardware innovations, this has started to change. At the heart of the PlayStation 4 in 2015, Andrew teamed up with Nathan Vos, Senior Technical Programmer at Guerrilla. Together, they developed the highly efficient open-world volumetric cloud system seen in Horizon Zero Dawn. The intricately detailed clouds framed Aloy’s world as hopeful and beautiful. It supported time of day changes and realistic animations, creating the feeling of a fully alive and breathing world.
This established the foundation the team would build on for Horizon Forbidden West.
evolution
In video games, clouds can help convey a mood. With the abundance of clear green waters and rugged cliffs, the clouds of Horizon punctuate the world with emotion. To achieve this, they had to be more than white wisps high above the Aloy’s head; they needed movement, variety and definition.
“We were inspired by artists who were part of the Luminism movement, such as the 19th century painter Albert Bierstadt. These painters had mastered the interaction between clouds and the land below, using light and detail to create space, producing truly spectacular landscape paintings.
“To recreate this effect in 3D, we had to develop a way to model the clouds. For Horizon Zero Dawn, we explored various methods of creating cloudscapes. Voxels are blocks that can build volumetric 3D clouds. We had actually created a cloud simulator and experimented with rendering three-dimensional “voxel” data in real time. »
“But technologically it was too early for that,” Andrew recalls. “The hardware and software just weren’t at the right stage of development. So we stuck to modeling the clouds in a render-efficient way that still gave 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 should be extended to support adding flying mounts in Horizon Forbidden West.
For the sequel, Andrew and Nathan improved the render quality of the base system used in Zero Dawn, extending it to support a new fog-like cloud that the player could walk through at low altitudes. This allowed for awesome atmospheres, like a super storm with sinister vortex motion and internal lightning effects. Now the clouds were a character in their own right, rumbling with atmospheric tension.
The next technical challenge
Naturally, the next step was to continue innovating this system for Horizon Forbidden West: Burning Shores. For the expansion, the team elevated the experience using voxel technology, among many other technical improvements around the world.
“The cloud systems we developed for Horizon Zero Dawn and Horizon Forbidden West were fast because they didn’t store clouds as 3D objects, but rather instructions on how to create 3D clouds from limited 2D information. The PlayStation 5 can handle larger data sets. So, after Forbidden West ended, we set to work writing a prototype voxel cloud renderer that could meet our quality standards and allow the player to fly through highly detailed cloud formations.
Achieving the balance between performance and quality when the player can be on the ground and high in the air was a tall order. Still, the prototype paid off, delivering dense, dynamic results at both low and high altitudes, a feat made possible through hard work, as well as the increased power of the PlayStation 5.
But creating a single cloud was far from creating an entire cloudscape.
Andrew had created what he called “Frankencloudscapes” – large cloud formations so the sky could be treated as a landscape by a terrain modeler. As a result, the cloudscape acted as both a background element and an environment to explore.
To make it work on the scale needed for Burning Shores, a Guerrilla Strike Team took on the challenge of flying through the clouds – the true test of performance and quality. Andrew partnered with Nathan and brought on Hugh Malan, a senior technology programmer.
The first hurdle they encountered was deeply technical: how to manage a huge amount of voxel volumetric data?
“Hugh and I divided this problem to conquer it. I developed a way to take low detail voxel data and add detail when rendering. During this time, Hugh worked on compressing the data so that it could be accessed faster from memory. Together, these processes made rendering volumetric voxel clouds exponentially faster. »
“But it still wasn’t fast enough,” Andrew recalls. “The most expensive part of this process was calculating cloud illumination, which in itself is complicated. To work around this issue, Nathan devised a method to reduce the render time to a speed that would work for both standard and high frame rate modes.
“It was also one of those rare situations where an optimization produced a better visual result. This allowed us to cast cloud-to-cloud shadows over a much greater distance, improving realism. At this point we had a method to render volumetric clouds from the ground and in the air right next to them. »
The second challenge was balance. “There’s a dance that real-time graphics engineers do to balance quality and performance,” Andrew continues. “Quality usually has a ‘cost’ in terms of processing. So whenever we improve the quality of our clouds, we must do so in a way that costs as much or less than the current cost of the cloud system.
To strike this balance, lead lead programmer and graphics engineer James McLaren helped the team understand how the code behaved at low levels on the PlayStation hardware itself. His expertise allowed them to take full advantage of the hardware by optimizing the code for the PlayStation 5. “James’ contributions were fundamental in the early stages of development, allowing Guerrilla to push the boundaries during production,” Andrew recalls .
Ultimately, the pieces add up to give the player the awe-inspiring feeling of soaring through and around a cloudscape as precise and varied as the land below. All from the back of their Sunwing.
What to expect at Burning Shores
On her way to the Burning Shores, Aloy will encounter machines and familiar faces. But she will also discover new ways to explore her world.
“It was important for us to make the experience fun and joyful in itself apart from the main gameplay. The clouds are not just immersive landscapes but an explorable landscape in themselves. Among the clouds, players will be able to explore tunnels , caves and other surprises that make flying fun,” says Andrew.
“The best part is that depending on when you try any of these features, the experience will be different. As the day progresses, the quality and direction of the light changes, hiding and revealing some of these characteristics and changing the feeling of each journey.
And I don’t want to spoil anything, but we hope you’re not afraid of a little lightning.
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