Metro Exodus’s Enhanced Edition is a very important game – it’s the first triple-A game we know of that’s built on technology that demands the inclusion of hardware-accelerated ray tracing hardware. To be clear, the new Metro is not a fully path-traced game built entirely on RT, but rather a hybrid renderer where global illumination, lighting and shadows are handled by ray tracing, while other elements of the game still use traditional rasterisation techniques. The bottom line though is that this is the foundation for developer 4A Games going forward: its games will require a PC with hardware RT graphics capabilities, while their console versions will tap into the same acceleration features found on the ninth generation consoles. And while 4A is the first developer to push this far into next generation graphics features, it’s clearly not going to be the last.
We’ve already reviewed the PC version of Metro Exodus Enhanced Edition and will be following up in due course with detailed analysis of the PS5, Xbox Series X and Series S renditions of the game. However, in putting together our initial coverage of the game, 4A Games were extremely helpful and collaborative in ensuring the depth and accuracy of our work. If you’ve seen our video breakdown of the title, you’ll have seen the behind the scenes editor shots showing level design workflow before and after the transition to ray tracing – but that’s just the tip of the iceberg. 4A were also very helpful in going deep – really deep – in explaining how their RT implementation works. On top of that, the developer gave us an excellent overview of the project: why it was time to move their engine to RT, how so many new technologies made their way into Metro Exodus Enhanced Edition, and why we need to wait a little while until the console versions are released.
It’s a wealth of in-depth information we’re going to be splitting into two deep-dive interviews. This week, we begin with a discussion with Metro Exodus executive producer, Jon Bloch, covering the general approach to developing the game and its new features. Next week, we’re catering to the hardcore graphics audience as 4A’s CTO Oles Shishkovstov and senior rendering programmer Ben Archard go into extreme depth on the development of the 4A Engine’s brand new ray tracing features.
Digital Foundry: What was the time frame and decision-making process about updating Metro Exodus on PC with the Enhanced Edition?
Jon Bloch: It kind of came to be when we were briefed in on the Gen 9 consoles supporting ray tracing. We knew that was going to be a cool opportunity to bring our RTGI tech to consoles, and in the process overhaul the systems further. And if we were doing that for console, we also had to take advantage of newer GPUs and expanded RT support in the PC space. We started planning it and looking at the systems we had already started to upgrade for our future titles, figured out what we could get done in time, and just started working on it – it was a pretty easy and unanimous decision for us and Deep Silver that this was a great opportunity to make Exodus even better and to bring some really cool upgrades to all our fans, not only the console ones. Work for this upgrade touched nearly all departments, but mostly programming. Artists needed to go back through and remove fake lights, polish and re-balance scenes, designers needed to make sure systems that rely on lighting like stealth still worked. This was not a fast or small undertaking, but we knew we had to do it as the opportunity was too great.
Digital Foundry: The switch to real-time ray tracing for so much of the game’s lighting is programmatically and visually profound, what were the production effects of this switch for development/artists?
Jon Bloch: One part of it is the response rate of the environment. If you have to bake lights or really run any heavy update process, there is going to be some amount of wait time to see the result of even a minor adjustment. This is the iteration period. The iteration period can make or break the entire development process. Around about a second, maybe a few seconds is fine: people can live with that. If it gets a bit longer, if there is maybe five to 10 seconds wait on something, people start getting afraid to experiment and they might miss out on cool discoveries that can really add something to the game. Any longer than that and you are into ‘getting up and going for a coffee’ territory and the whole thing collapses. Ideally you want to see the results of your changes instantly. That’s why we have put so much focus on ensuring that every graphical feature we have can be achieved in real-time.