AMD, Developers Embrace Forward Rendering in Unreal Engine 4 to Improve VR
Compromise. It’s something many VR developers today deal with in their ongoing quest to nail the right mix of technical features and computational power for the best balance of performance and visual fidelity. Many of today’s big game engines use a technique called deferred rendering. Deferred rendering does all of the geometry work first and then shades pixels last to save work. That worked well on the last generation of consoles, but it’s not a great fit for VR. With the forward rendering path in Unreal Engine 4, developers have more choice in how they render for VR, helping to achieve a stunning looking game while delivering the high frame rates necessary for a good experience.
Discussed on stage at AMD’s “Capsaicin” webcast and press event at the 2017 Game Developers Conference, the forward rendering path provides a strong alternative to the popular deferred rendering method, allowing developers to hit the demanding frame rates necessary for smooth VR experiences with improved image quality. Forward rendering has been showcased in games such as Epic Games’ own Robo Recall, and upcoming VR titles from awesome developers like Survios, First Contact Entertainment, and Limitless Studios.
Technically Speaking: Deferred vs Forward Rendering
Deferred rendering has a performance cost for each frame, and it has higher memory requirements. Deferred rendering does support some nice features like screen-space reflections, but those features are generally too costly to use given VR’s 90FPS requirement. In addition, VR needs high-quality edge smoothing, primarily due to current HMD resolutions.
Deferred rendering unfortunately doesn’t mix well with multisampled anti-aliasing because there are performance and image quality issues. But MSAA is arguably the best AA technique for VR. Post-process AA methods like FXAA don’t work terribly well with stereo views in VR. If you’ve tried a game that uses it, you’ll know it does not look good.
All told, we feel that deferred rendering exacts a toll in terms of time, memory, and image quality in VR, and the payoff just isn’t there. The alternative here is to adopt a form of forward rendering. Interestingly, it’s not a new
technique. If fact it’s how GPU rendering started. It’s lighter weight, simpler, and faster. Also, forward rendering works nicely with MSAA, letting us improve edge quality very efficiently. So we think forward rendering is often a better fit for VR applications.
We’ve been working diligently to enable a forward rendering path in Unreal Engine 4.15, giving developers more choice in how they develop VR games. We have a number of VR development partners who are using this engine, and we’re showing the performance benefits during GDC. “AMD has been on a continuous mission to make VR accessible to as many people as possible and the forward rendering path in Unreal Engine 4 is a big step in that journey,” said Raja Koduri, Senior Vice President and Chief Architect, Radeon Technologies Group, AMD.
“Anyone who has experienced Epic’s Robo Recall will immediately attest to the benefit of forward rendering in VR. We are working with VR developers to explore the benefits of forward rendering, which can result in beautiful, high-performing games on Radeon graphics.”
AMD is working with leading game developers to explore the benefits of forward rendering in VR games, including:
• Survios: Since its Early Access release last year, Survios’ critically-acclaimed and awardwinning game Raw Data has become a must-have title for all VR gamers. At AMD Capsaicin, Survios unveiled their highly-anticipated new title: Sprint Vector, which makes use of Unreal Engine 4.15 and forward rendering. An intense adrenaline platformer, Sprint Vector uses a unique intelligent fluid locomotion system to propel players through high-speed head-to-head races through challenging interdimensional obstacle courses.
• First Contact Entertainment: First Contact Entertainment’s breakout game, ROM: Extraction is one of the most visually appealing and exciting VR releases, debuting this past December to rave reviews. Available today, First Contact Entertainment is releasing “Overrun,” a new content expansion to ROM: Extraction that makes use of forward rendering for unprecedented performance.
• Limitless Studios: Directed by Matthew Ward and built in virtual reality using the Limitless VR Creative Environment, Reaping Rewards is an interactive VR experience exploring the emotional choices of a young Grim Reaper as you learn about life and death from your mentor. This interactive character-driven story harnesses forward rendering to bring the experience to life.