A few months ago, Gaijin Entertainment introduced path traced global illumination to the PC version of War Thunder, significantly improving visual quality over the game's previous ray traced global illumination solution.
In doing so, War Thunder joined an extremely elite club of games that feature real-time path tracing: Cyberpunk 2077, DESORDRE, Alan Wake 2, Black Myth: Wukong, Indiana Jones and the Great Circle, F1 25, DOOM: The Dark Ages (whose developers have just opened on on their path tracing implementation), and FBC: Firebreak, Remedy's second game on this list.
We contacted Gaijin to organize an email interview that would dive deeply into this tech advancement for War Thunder and the whole Dagor Engine (also used in other games published by the studio, such as the MMOFPS Enlisted). At last, we received the responses back, courtesy of Anton Yudintsev (co-founder of Gaijin Entertainment), László Perneky (lead programmer), and Gergo Horvath (programmer). You can find them after the embedded footage.
How long did it take for you to implement Path Traced Global Illumination in the Dagor Engine? Was it complex to go from ray tracing to path tracing?
László Perneky: The ray tracing framework we have is very flexible. We can reconstruct any surface on the whole map with quality very close to rasterized ones, and we keep the ray traced scene in sync with the rasterized scene. With this at our disposal, the first working prototype went fast, in just a couple of weeks. But then the devil is in the details. We had to make sure the results were good in all cases. When rendering airplane cockpits, you need special considerations compared to rendering a tank from behind. We needed to prepare PTGI for all the cases the player can encounter.
Performance is also a big concern. PTGI replaces RT ambient occlusion, which gives us some headroom but is also much heavier, so we needed to make tons of small decisions on optimizations. In the end, we spent about a month on the initial version, but we are still tweaking/refining it ever since.
Will the open source version of the Dagor Engine be updated with path tracing support?
Anton Yudintsev: Probably by the end of the year.
Do you consider the Leviathan update to have added the final version of PTGI, or do you believe there is still room for improvement? If so, is it for quality, performance, or both?
Anton Yudintsev: There is almost always room for improvement for both quality and performance. While the idea of Path Tracing itself is “uber-solution”, implying that we achieve the best possible result by tracing lighting data for each pixel, in reality, a naive approach would be prohibitively slow (~8 million rays with few bounces each), so virtually all real-time solutions use some form of temporal upscaling and so, some kind of denoising. And that would be an area of improvement for visual quality. Also, each game uses its own set of tricks for achieving faster ray-tracing itself (especially for foliage, etc). Performance-wise, it is always possible to do something, although eventually, efforts start to provide diminishing returns. That said, we are rather satisfied with both quality and performance for such quality achieved.
You wrote that you are planning to add support for Opacity Micro-Maps (OMM) and Shader Execution Reordering (SER). How much of a performance boost do you expect from those additions? Also, do you have an ETA on when they might be introduced to War Thunder?
László Perneky: Absolutely. In fact, both are underway. For SER, we need to change our ray generation method, as to use it, there are some constraints, like you can’t use it in compute shaders. For OMM, we already have a working prototype, and while it doesn’t do wonders, it brings decent improvement in tracing performance, especially with areas with denser foliage. Microsoft recently made both of these features part of the core Direct3D system. We are still waiting for the final GPU drivers with support for these technologies. But by the time those arrive, we can probably finish the work on them in Dagor and War Thunder and release these features early next year.
What do you think about DirectX's Work Graphs (released to developers a year and a half ago)? Are they as important as Microsoft is claiming? Will you implement them for your engine?
Anton Yudintsev: This is the long-awaited step to a more GPU-driven rendering pipeline. In some cases, it can provide significant GPU workload optimization and almost always free some CPU. Unfortunately, its benefits are only possible on rather new hardware. We do want to implement Work Graphs support as well in the upcoming years.
Could PS5 Pro support some version of path tracing? Also, do you have any future improvements coming to the PS5 Pro version, and if so, which ones?
László Perneky: Technically, it could; the only question is with performance. It is a decision for the future, though. First, we focus on releasing RT support for consoles, with all the effects except PTGI (hopefully very soon). Then, we will have a better picture of how much GPU budget we have to include PTGI and if we can make changes to it to fit that budget.
Are you adding AMD FSR 4 support at some point?
Gergo Horvath: FSR4 is a high priority for us as it is an often-requested feature from players. We have had some divergence regarding upscaling and frame generation technologies supported by each of the games. Even though they are using the same engine. We had XeSS-FG and XeLL added to WT as well as AMD FSR3 with frame generation to War Thunder and now Enlisted is lagging behind. We are planning to remedy the situation by converging support of these technologies in all of our games by the end of the year, and AMD FSR4 will also be part of that package for PC. If and when FSR4 would be available for consoles we will already be ready.
Will Enlisted also receive a PTGI update? If so, is there an ETA?
Anton Yudintsev: Yes, it is planned to have PTGI in Enlisted as well – internally, we do have a running version with it already. Although our current GI solution is giving very similar results to PTGI with significantly higher performance, it is always good to be able to compare to the “ground truth” solution. We aim to release it this year, though no hard deadline yet.
The Nintendo Switch 2 is out now, and it's being sold like hotcakes. Are you considering a Switch 2 port for War Thunder and/or Enlisted?
Anton Yudintsev: We’re always eager to be among the first to support new devices, so we’re definitely considering Switch 2 versions of our games. Unfortunately, right now we’re still waiting for the requested Switch 2 dev kits.
Thank you for your time.
About the author: With over two decades of experience in gaming journalism, Alessio Palumbo has led the gaming vertical at Wccftech since August 2015. He started working at a young age for Italian websites like Everyeye.it, Gamestar.it, Nextgame.it, and Multiplayer.it before kickstarting the indie English-language publication Worlds Factory as its founder and Editor in Chief. In the last decade, he has coordinated the overall output of Wccftech's gaming section, managed PR relations, assigned reviews, produced daily news coverage, edited gaming content as needed, and delivered game reviews. Arguably, his trademark content is the long series of exclusive developer interviews that have been cited by Wikipedia and by the biggest news media and gaming publications. His passion for technology also makes him knowledgeable when it comes to gaming hardware and tech. His favorite genres include RPGs, MMORPGs, and action/adventure games.
Follow Wccftech on Google to get more of our news coverage in your feeds.
