Hardware accelerated ray tracing is now firmly established in triple-A titles on PC and with the transition to next generation Xbox and PlayStation hardware, consoles can now join the party. Watch Dogs: Legion is the first DXR-enabled title we’ve seen that also features ray tracing on consoles – which raises the question: to what extent can the new machines match up to existing PC hardware? What kind of compromises are required to bring RT to consoles – and what happens when we retrofit those cuts to the PC version? Let’s just say that the answers are illuminating.
Hardware RT in Watch Dogs Legion is used for reflections, replacing the standard system based on a combination of screen-space reflections and cube maps. To make that clearer, cube maps are essentially non-dynamic ‘probes’, capturing environment detail and baking them into a texture wrapped around a cube – and typically thousands of them are generated in any given scene, drawn upon when needed by the game engine. Screen-space reflections capture what’s on-screen, mapping that information into reflective surfaces like glass walls and puddles. This combination is often convincing enough but is rarely satisfying in reflecting moving objects (like people milling around the city) or in showing detail that isn’t currently on-screen. Ray tracing is expensive but solves all of these issues – and Marvel’s Spider-Man: Miles Morales is the best console rendition we’ve seen to date, up to a point.
Watch Dogs: Legion perhaps lacks the full RT spectacle of Insomniac’s efforts but it does have its own plus points. Unlike Spider-Man, there are reflections within reflections, so the reflection of a puddle on the ground, for example, will show reflective properties. Also, the geometry in reflections looks to be the same level of detail and precision as those in the primary view – Miles Morales has a lower precision ‘RT city’ from which to draw its reflections. However Ubisoft’s implementation also has plenty of similarities with the PS5 exclusive. Xbox Series S and X are using stochastic reflections much like Insomniac’s tech, so they will technically produce more realistic surface reflections than other simpler types of ray tracing. Also, the ray traced reflections in Watch Dogs: Legion add to transparencies – so glass materials look very realistic. Put simply, it’s a big upgrade from a visual perspective, especially for a cityscape rich in reflective surfaces.
Hardware RT is computationally expensive and right now the consoles have no AI upscaling technologies like DLSS available to mitigate the performance hit and this presents a problem. Even on my optimised settings, the PC version of Watch Dogs: Legion was managing just slightly above 30fps with ray tracing set to the lowest setting at 1440p internal resolution when using an RTX 2060 Super. Series X renders with dynamic resolution scaling between 1440p and 2160p, with Series S coming in at 900p to 1080p. So how is Ubisoft achieving this? Is it a fully featured RT implementation comparable with PC? Well, the answer is no – and we know this not just from our eyeballing but also from the Watch Dogs: Legion PC version, which rather helpfully contains of the settings data for every rendition of the game.