We just learned a whole lot more about the upcoming PS5, thanks to another interview with system architect Mark Cerny . In it, he delved a bit more into how the PS5 will deal with ray tracing⁠—the ultra-realistic lighting effects that have been all the rage on gaming PCs this year⁠. Let's take a look at what this technology actually is, why you should care, and what it might look like on Sony’s upcoming console.

Real-time ray tracing demonstrated in Battlefield V at an Nvidia press event.

What Is Ray Tracing?

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You can see a visual explanation of this in Disney's Practical Guide to Path Tracing, showcased in the GIF above.

So What’s Special About Ray Tracing GPUs for Gamers?

To understand this new tech, it helps to take a brief look at what has preceded it. Modern video games have long used a technique called rasterization to generate the image on your screen. The way it works is your computer looks at a 3D scene and calculates the distance to certain objects, where light is coming from, and which objects are in front of others. Using that information, it determines what color each pixel should be on your monitor, drawing the scene dot by dot as a 2D image.Over time, developers have improved on this tech quite a bit, giving objects the ability to cast basic shadows based on light sources, or using tricks like ambient occlusion to add extra shadows independent of light sources. But most games don’t truly simulate the way light behaves in the real world - they fake it with one technique or another - making it hard to generate truly realistic shadows and reflections. (That’s why you rarely see mirrors in video games, and when you do, the images within them are generally very crude.)Ray tracing is a rendering technique that aims to simulate the way light bounces off objects, in turn creating more realistic shadows, reflections, and lighting effects. In an interview with Gamers Nexus , NVIDIA’s Tom Peterson described it as a physics-based way of creating images, as opposed to an artistic way of creating images.In the real world, a light source—say, the lamp in your bedroom—produces photons that bounce around the room until they reach your eye. Ray tracing performs this process in reverse, tracing individual rays from the scene’s “camera” and tracking how each ray intersects with different objects, cast shadows and reflections, and make its way back to the light source. This ensures the computer isn’t wasting processing power on objects the camera doesn’t see, while still producing far more realistic lighting effects. Disney made a great video explaining this process for path tracing, which is similar to ray tracing, which we've sampled in the GIF below This technique has been around for many years, and you’ve seen it countless times in movies with computer-generated special effects. Hollywood uses render farms to calculate ray tracing for scenes since they're working with massive data sets and doing huge numbers of rays for entire scenes. It can take hours or days to render even a short scene in a CG film that uses ray tracing. In the past, the amount of calculations required made it impossible to do in video games since it needs to be done in real-time to not affect gameplay.

Ray tracing may be common in Hollywood blockbusters, but those effects are created on expensive render farms, and even then it can take hours (or even days) to render a single frame due to the complexity of it. Video games, on the other hand, have to be rendered on your home console or PC, in real-time, at 30 to 60 frames per second. That means advanced lighting techniques like this have never been easy to implement. In fact, when IGN first shared Nvidia's initial Star Wars Ray Tracing demo from GDC in 2018, one commenter noted, "It's a good demo but this lighting isn't possible in real-time on affordable PCs at the moment, probably will be in 5 to 10 years though."

How Does Ray Tracing Affect Gaming Performance?

That demo was running on four Tesla V100 GPUs, and at Nvidia’s event five months later, the company showed it running on one RTX Quadro card. Sure, a Quadro is still six times the price of the gaming-focused RTX 2080 Ti , but it's a huge step forward in a remarkably short amount of time, and the fantasy of real-time ray tracing being possible at home is racing toward reality.Nvidia’s GeForce RTX family of GPUs, released last year, were the first consumer-oriented, gaming-focused graphics cards that support real-time ray tracing — but they came with some caveats. These cards make use of what Nvidia calls a “hybrid rendering model” that combines ray tracing with rasterization techniques, thanks to dedicated ray tracing cores designed to calculate the intersection of each ray. It also uses special de-noising algorithms and dedicated artificial intelligence hardware, called “Tensor Cores,” to reduce the number of rays that need to be traced. In other words: they’re still cheating a little bit, since these cards won’t necessarily ray trace entire scenes in real time, but the results are a significant step forward from current rasterization methods. The slide below is how Nvidia presented its new rendering model compared to just straight rasterization, where the GPU is merely converting the shapes to dots on your screen.These RT and Tensor cores are not required for these calculations to happen, however. Nvidia eventually released ray tracing support for older GTX cards (at least, GTX cards based on the Pascal and Turing architectures), which don’t have those extra RT or Tensor cores. Ray tracing without those cores is much less efficient , though, meaning you’re likely to suffer even worse performance hits than you would with ray tracing on an RTX card. And that’s what’s holding up ray tracing from being ubiquitous: performance.

When you enable ray tracing in a PC game that supports it, you’re going to see lower framerates than you would with ray tracing turned off. When we played a work-in-progress version of Shadow of the Tomb Raider and Battlefield 5 with Ray Tracing enabled last August, we weren’t able to hit a constant 60 frames per second at 1920 x 1080—more like 30 to 50 frames per second, even though we were using an RTX 2080 Ti. Since then, driver updates and game patches have improved performance quite a bit, with 60 frames per second much more easily achievable in Battlefield V, depending on your settings. But you’ll still see lower performance than you would with ray tracing disabled: some games take a hit as large as 40%, while others might only see a 15% decrease in framerate. This will vary from setup to setup, and even from game to game.

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What Will Ray Tracing Look Like on the PlayStation 5?

That’s because different games implement ray tracing in different ways. Battlefield V, for example, uses ray tracing to produce more realistic reflections on the side of metallic objects, or in puddles on the ground. Shadow of the Tomb Raider uses ray tracing primarily to improve the quality of its shadows. Metro: Exodus, on the other hand, uses “global illumination” to produce more realistic lighting all around you, which leads to a heavier performance hit than those other games.

Nvidia’s real-time ray tracing technology has only been around for a year, and both Sony and Microsoft have already promised ray tracing support on the PlayStation 5 and Xbox Scarlett. Not only that, but Cerny said in his most recent Wired interview that there will be “ray-tracing acceleration in the GPU hardware,” which means AMD⁠—who’s manufacturing the guts of the PS5⁠—may be crafting the PS5 GPU specifically for this purpose, the way Nvidia did with the RT and Tensor cores on its RTX line of cards. That’s a good sign for the PS5’s performance.

PS5 Games We Think Might Already Be In Development 8 IMAGES

Even with that added efficiency, though, I wouldn’t let your expectations get too wild just yet. Nvidia’s cheapest RTX card, the RTX 2060, has an MSRP of $400⁠—the same as the PS4’s original launch price. To build a ray-tracing capable PC, you’d need to spend at least a few hundred more than that, which is getting pretty expensive for a console. Sure, ray tracing hardware will probably drop in price by the time the PS5 launches in 2020, but it’s unlikely that the PS5 will compete graphically with a modern ray-tracing capable gaming PC unless Sony is targeting a daringly high price point Instead, I’d expect that the PS5 will do even more of that “cheating” we talked about earlier⁠—tracing fewer rays and using post-processing to blend the effect within the scene, or only using ray tracing on shadows or reflections of certain objects. (And I wouldn’t be surprised to see lots of those games sticking to ~30 frames per second.) Sony also said earlier this year that ray tracing could also be used for the PS5’s 3D audio implementation, tracing sound waves around the scene to more accurately pinpoint where certain sounds are coming from—and thus create more convincing surround effects, so you know where every enemy is hiding.It’s possible we’ll be proven wrong when Sony comes out with its next-gen behemoth, but I’d rather be pleasantly surprised than disappointed by my own sky-high expectations. Just like the PS5’s 8K gaming claim is likely to be a bit exaggerated , Sony’s ray tracing promises are intended to get you excited about the latest gaming buzzwords . It’ll undoubtedly be a step up from the PS4, though, and that’s enough for me.

Now that you know that "Ray Tracing" isn't the name of a new IGN editor, be sure to check out this full roundup of PS5 details and features , too.