Cyberpunk 2077: The tech interview - "ray tracing proved to be quite a challenge"

Nvidia and CD Projekt Red cooperate heavily on Cyberpunk 2077 and the technical partnership includes four ray-traced effects along with performance-enhancing NVIDIA DLSS 2.0 tech. As for now Cyberpunk 2077 should feature Ray-Traced Diffuse Illumination, Ray-Traced Reflections, Ray-Traced Ambient Occlusion and Ray-Traced Shadows. We had the chance to get some more technical information about the implementation of RT effects.

➤ PCGH: Cyberpunk 2077 looks like a very good fit for ray tracing, considering there's quite a lot of clean and shiny surfaces, some high-contrast environments, a dynamic day-and-night-cycle and also quite a lot of open areas with a lot of detail where bounce-lighting would probably work and look pretty well. But maybe you can tell us with your own words, why you chose to implement ray tracing in Cyberpunk 2077 - and what do you consider the biggest gain this technology brings to your game?

Jakub Knapik: In its native mode, so with DXR features disabled, our engine is equipped with global illumination, hence it supports bounced lighting in a platform-agnostic way. Our goal was to create a rendering platform that would use PBR (physically-based rendering) rules and a realistic approach to lighting on all platforms. That paradigm made ray tracing a natural extension of the idea, the next step in its evolution. We worked on a hybrid solution that is added on top of our already existing setup, replacing some of our lighting subsystems with ray-traced equivalents. That gave us basic parity, meaning we don't have to make a separate lighting variant, and at the same time — a huge quality boost in some areas we found the most useful for Cyberpunk 2077 (jetzt kaufen ), ones we can further tweak to our needs.
Our interview partner: Jakub Knapik (CDPR) Quelle: CD Projekt Red
Currently, we use sun soft shadows, a solution that gives us incredibly detailed results, capable of picking up any objects visible to the eye and simulating the natural phenomenon of softening shadows based on distance. We use a ray-traced skylight that works with our proprietary global illumination system, producing a super realistic ambiance coming from the sky and clouds. We also use emissive surfaces like screens, neons to emit realistic soft lighting with perfect shadows during the night. Additionally, and also quite obviously, we take advantage of all the benefits of ray-traced ambient occlusion and we are currently working on ray-traced reflections. As for the biggest benefits, I think they chiefly come from the precision of 3D space ray tracing versus more traditional screen space solutions.

➤ PCGH: Since we last saw a live build of Cyberpunk 2077 at Gamescom 2019 you've added quite a lot of new ray tracing effects, for example reflections and indirect illumination. And since this is your own engine and you presumably also work on your own tools for it: How hard is it to implement ray tracing into a game-engine?The implementation of ray tracing (...) proved to be quite a challenge.

Jakub Knapik: Overall, the implementation of ray tracing into the game engine on a practical level, with all the needed parity and care for our in-engine systems, proved to be quite a challenge. That said, I think the difficulty is something that's very case-dependent. Every engine is molded to serve specific needs. Our own was set up to enable us to depict the incredible complexity of Night City, with its vast verticality and enormous amounts of assets across the city. All that with dynamic global illumination working in real-time with all local lights, a dynamic day and night cycle, as well as changing weather states.

➤ PCGH: You've opted to use Direct X 12 Ultimate. Will there be a fallback so gamers who are still running Win 7/8.x can also play? Was there a decision between the lower-level APIs DirectX 12 and Vulkan, and if so, why did you pick DX12?

Marcin Gollent: Thanks to the introduction of DX12 support for Windows 7 SP1 that Microsoft introduced last year, the game will run on this system. We do, and will continue to, test Cyberpunk 2077 on Windows 7 in an attempt to iron out any edge-cases that might arise. Unfortunately, Windows 8 didn't receive its variant of DX12 libraries.
Our interview partner: Marcin Gollent (CDPR) Quelle: CD Projekt Red
Regarding DX12 Ultimate, Cyberpunk 2077 will work absolutely fine with all DX12-compatible GPUs. What the "Ultimate" feature set does is it allows us to do more if the hardware allows for it. We opted to go with DX12 for two main reasons. Firstly, it is the standard API for the Xbox platforms, and with the game also coming to Xbox One, we naturally wanted to have it implemented as soon as possible. Secondly, it is the birthplace of DXR, and given we had plans to invest in DXR very early on, that made the choice to go with DX12 a pretty straightforward one.

➤ PCGH: We've recently seen some quite impressive ray tracing demos from Sony running on the upcoming PS5. They've even managed to get raytraced reflections working (at least somewhat). Are there plans for Cyberpunk 2077 to also support raytracing on the upcoming console-generation?
Ray tracing is going to make the world-building process easier and less technical.
Marcin Gollent: At release, Cyberpunk 2077 will work on these consoles in backward compatibility mode. We recently announced that everyone who purchases the PlayStation 4 and Xbox One versions of Cyberpunk 2077 will be eligible to download a free next-gen upgrade that will take advantage of PlayStation 5 and Xbox Series X hardware, but it is too early to talk specifics at this time. Right now we're working very hard to make Cyberpunk 2077 look, feel, and most importantly play great on PC, as well as PlayStation 4 and Xbox One.

➤ PCGH: Ray tracing looks like it's going to stay. How do you reckon the technology to advance in the future? Do you think the majority of games will take advantage of technology and how do you think will it impact game-design and world-building?

Marcin Gollent: We believe that, at the very least, ray tracing is going to make the world-building process easier and less technical. It should allow the lighting artists to focus on their vision more, and be less distracted by the technicalities. Technicalities required, for example, to set up a game location without custom tweaks needed to make lighting work within more complex architecture. It holds the promise of making the world-building and art direction workflows simply faster, allowing for more predictable iterations. More swift iteration usually allows for the final result to feel even more polished and better tell the story that the game's environments are designed to tell. We also believe that there is still more to discover on how to use ray tracing in other fields of rendering in the future.

➤ PCGH: Thanks for the interview!