Gamescom 2019: did ray tracing finally find its killer app?
Hands on with the new range of RTX-accelerated games.
There were many highlights for Digital Foundry at this year's Gamescom, from the impressive Switch line-up to the hugely impressive retro-inspired Wrath: Aeon of Ruin. We'll be covering both of those soon - but with the absence of any next-gen console reveal, it was Nvidia that provided the most tantalising glimpse of the future of games technology. Almost one year after its RTX video cards launched, there's the sense that support for hardware-accelerated ray tracing is gathering momentum and in Minecraft RTX, there's a near-total implementation of RT that sets the imagination on fire.
It's a far cry from the launch of the RTX cards at the tail end of September last year - a debut for new Nvidia hardware that fell short of its potential due to a lack of software support. Rasterisation performance gains over existing Pascal-based GPUs were minimal, meaning that the experience of gaming using, say, an RTX 2080 was virtually interchangeable with the existing GTX 1080 Ti in the same price bracket.
Ray tracing demonstrations at Gamescom 2018 showed rich potential, but nothing launched alongside the hardware - and even when showpiece game Battlefield 5 arrived with RT support, it took weeks of further development to get performance into the right place. More than that though, the briliant Metro Exodus aside, it was difficult to see where the momentum would come for further ray tracing support. Where were the big triple-A launches with RTX features?
What's clear from this week's Gamescom showing is that lessons have been learned and the outlook for RTX has improved considerably, which at the same time helps to lay the groundwork for ray tracing support in the games - and the consoles - to come. Kicking off with the big triple-A titles, Nvidia's statement of intent from both E3 and Gamescom is clear: the most prominent releases will be receiving ray tracing support. The extent of that support obviously varies on a case-by-case basis, but the fact that games including COD Modern Warfare, Watch Dogs Legion, Dying Light 2 - and of course, Cyberpunk 2077 - will receive ray tracing features is a big deal.
In fact, it all kicks off next week with the arrival of Remedy's Control - a visually stunning game that delivers a night and day improvement with its ray tracing features enabled. Another example of 'jam today' ray tracing support comes from the freshly minted Two Colonels DLC for Metro Exodus - 4A Games' stunning global illumination implementation is bolstered with new support for emissive lighting - it's not just the sun or the moon that defines the GI now, in-game surfaces do too, and 4A is nice enough to send you underground with a flamethrower to test it out.
But it's the incredible work of Mojang in fully integrating path traced lighting into Minecraft that really highlights how transformative ray tracing is when pushed to its fullest extent. Rather than concentrating on specific effects like reflections, ambient occlusion or global illumination, Minecraft delivers the full path-traced experience. Standard 3D rasterisations technicals are barely touched - the entire scene is rendered based on the way light travels and how it interacts with different surfaces and the properties of their materials. It works in real-time owing to the simplistic nature of Minecraft's visuals, but it delivers a radically transformative effect in graphics. You look at this and you start to get an idea of the trajectory of video game graphics in the years (more likely decades) to come.
While this kind of totally transformative effect can't sit within a cutting edge game like, say, Cyberpunk 2077 (we simply don't have the GPU power) it does serve to highlight how path tracing can still play a role in the present day fortunes of the RTX line of graphics cards. The PC platform is decades old and 3D accelerated hardware hit the mainstream in 1996, with the 3DFX Voodoo Graphics products quickly becoming fan favourites. By today's standards, the games are primitive - but path traced visuals applied to ancient game engines can produce some astonishing results.
It started with Christoph Schied's Q2VKPT, which took the open source code for Quake 2, replacing the rasteriser completely with a path tracer based on Vulkan and using RTX hardware acceleration. The results were good enough for Nvidia to take the codebase and improve it with a range of further features designed to leverage the strengths of path tracing, from improved textures to water caustics to new skyboxes (with enhanced atmospheric scattering effects) and a full time of day cycle.
It's a brilliant demonstration for hardware-accelerated ray tracing, to the point where you have to wonder in hindsight how the RTX launch may have shaken out were select PC classics 'remastered' with path tracing while we waited for the triple-A behemoths to arrive. Suffice to say, the impression we got from Gamescom is that further back catalogue PC classics are likely to receive the same treatment - and we can't wait.
As for the titles on display at the show, Minecraft was the obvious stand-out while the sense remains that in a lot of cases, ray tracing is a bonus 'value add' rather than a transformative technology. Wolfenstein Youngblood shows id Tech 6 receiving reflections and transparent reflections, which add to the presentation in a pleasing way though many may argue that the standard 'fakery' still holds up well enough. Watch Dogs Legion seems to replace with screen-space reflections with far more accurate RT, but the cut-off point on what gets reflected can present some oddities. Remedy's Control though? In a word: wow.
Call of Duty: Modern Warfare has managed to provoke an interesting response. Standard shadows are replaced with hardware-accelerated RT versions, which has led to some interesting observations from some of our audience on a perceived 'downgrade' - when the reality is that a realistically rendered ray traced shadow is obviously more accurate than a razor-sharp, non-graduated shadow map. It's a fascinating example of how some aspects of video game graphics rendering have become the norm to the point where more realistic replacements are considered inferior!
While ray tracing is exclusively the preserve of Nvidia graphics technology right now, the work done by the developers of today is invaluable for the hardware and the games of tomorrow. What's clear is that game-makers can't just flip a switch in-engine and enable full path traced lighting with no performance penalty - there are limits, clearly. The RTX launch has clearly demonstrated that it takes time for developers to get to grips with hardware acceleration and to build scalable solutions that work across a range of kit (our benchmarks suggest that across the RTX stack, a 2080 Ti has around 2x the raw ray racing power of a 2060).
AMD graphics cards supporting the DXR API are in development, meaning that when they do appear, there should be a ready-made library of software to support them. Meanwhile, hardware-accelerated ray tracing is set for inclusion in some form in the next-gen consoles, so the stage is being set for a gradual evolution in graphics - but perhaps more importantly, with the new consoles setting the base line, key aspects of actual game design can be built around the opportunities ray tracing represents.
There's still very much the sense that we're at the formative stages of the ray tracing revolution, and as impressive as Nvidia's Gamescom line-up was, there's still the sense that RT is a value-added extra as opposed to a must-have feature. Will that perception change any time soon? Well, Remedy's Control is set for release this week on Xbox One, PS4 and PC. It's a multi-platform game with one of the most fully featured ray tracing implementations we've seen, available on day one. We'll be covering it as soon as we can.