Battlefield V Creators: We Toned Down Ray Tracing for Performance, Realism

On September 6^th, EA DICE’s Battlefield V officially exits its closed alpha stage and becomes available for everyone to play as an open beta. The game won’t yet support real-time ray tracing, but that’s fine; Nvidia’s Turing-based GeForce RTX 2080 and 2080 Ti graphics cards don’t start shipping until September 20th.

When Battlefield V launches two months later, though, ray tracing will be part of its day-zero patch. Tom's Hardware had the opportunity to sit down with Christian Holmquist, technical director of DICE, to talk about the company's plans for Battlefield V and some of the game's technical capabilities. One key nugget: the company had to dial back the ray tracing technology in order to increase frame rates and make the images look more credible. 

The stage demo given by DICE’s team during the Nvidia Gaming Celebration event in Cologne, Germany yielded several impressive examples of how ray tracing improves the realism of what you see in games compared to traditional rasterization techniques like screen space reflection (which is a performance-intensive feature unto itself). With everything moving in slow motion, toggling between ray tracing on and off, the result was truly stunning. We cannot wait to see gaming realism stepped up significantly by the application of real-time ray tracing.

During the demo, certain effects did stand out as if they were exaggerated to showcase Nvidia’s RTX technology, though. Windows in the Rotterdam map were perfectly reflective and paint on the cars was mirror-finished.

DICE’s Holmquist assured us that ray tracing doesn’t change anything about the way art assets are handled in Battlefield V. "What I think that we will do is take a pass on the levels and see if there is something that sticks out," he said. "Because the materials are not tweaked for ray tracing, but sometimes they may show off something that’s too strong or something that was not directly intended. But otherwise we won’t change the levels—they’ll be as they are. And then we might need to change some parameters in the ray tracing engine itself to maybe tone something down a little bit."

Indeed, in one specific scene, DICE dialed back the reflectivity of walls in a room to help improve performance after it was observed that ray tracing hit the frame rate too hard.

DICE is also putting in a lot of work to make sure PC platforms don’t bottleneck Nvidia’s GeForce RTXes. During our interview, Dave James of PCGamesN asked Holmquist what DICE was doing to minimize the impact of ray tracing on Battlefield V.

"So, what we have done with our DXR implementation is we go very wide with a lot of cores to offload that work," Holmquist replied. "So we’re likely going to require a higher minimum spec and recommended spec for using RT, and that was the idea from the start. It won’t affect the gameplay performance, but we might need to increase the hardware requirements a little bit. And going wide is the best way for the consumer in this regard because you can have a four-core or six-core machine. It's a little bit easier these days for the consumer to go wide with more threads than have higher clocks."

It sounds like the engine is optimized for six-core CPUs with simultaneous multi-threading but may work well on 4C/8T processors as well.

GeForce RTX owners should get the option to turn ray tracing off. However, there is no DXR (DirectX Ray Tracing) fallback path for emulating the technology in software on non-RTX graphics cards. And when AMD comes up with its own DXR-capable GPU, DICE will need to go back and re-tune Battlefield V to support it.

Holmquist clarifies, “…we only talk with DXR. Because we have been running only Nvidia hardware, we know that we have optimized for that hardware. We’re also using certain features in the compiler with intrinsics, so there is a dependency. That can be resolved as we get hardware from another potential manufacturer. But as we tune for a specific piece of hardware, dependencies do start to go in, and we’d need another piece of hardware in order to re-tune.”

We also pressed the DICE team on performance differences between its DirectX 11 and DirectX 12 code paths, the former of which is considered faster on Nvidia hardware. Holmquist continued, “We did optimize some paths of DX12, but since most of this work is in the DXR API, what we did was that we made sure none of that was bottlenecking our throughput. So, playing DX12 performance will be similar to what we had in Battlefield 1”.

The option to use DirectX 11 in Battlefield 1 also appealed to gamers with multiple GPUs, since AMD’s CrossFire and Nvidia’s SLI both worked to improve frame rates. Unfortunately, neither technology functioned under DirectX 12. This continues in Battlefield V, as DICE has no plan to support multi-GPU configurations.

We’re actually a bit surprised that DICE eschewed multi-GPU support. Right now, DICE is targeting 1920x1080 at 60 FPS with RTX enabled. Surely, a second GeForce would be a great way to scale such a taxing workload, particularly since Nvidia offers up to two NVLink sub-links with 100 GB/s of bi-directional throughput for card-to-card communication.

While we couldn’t get anyone at Nvidia to comment on dependencies that would preclude a DXR-enabled game from rendering properly in AFR mode, we did ask Epic Games’ Tim Sweeny about hypothetical limitations.

“Multi-GPU scenarios are all workable for ray tracing. There aren’t any new dependencies between frames. The only limiting factor is cost," Sweeny said.

So perhaps as DXR-capable hardware proliferates, game developers will see more upside to supporting multi-GPU configurations, making smooth ray traced performance at 2560x1440 and 3840x2160 realistic sooner than later.