What is ray tracing, and how will it change games?

Nvidia's new GPUs are all about ray tracing. Here's why that matters

Nvidia

Nvidia announced its new RTX 2070, 2080, and 2080 Ti, and the latter two are out in the wild. These video cards offer an across-the-board performance leap above the GTX 1070, 1080, and 1080 Ti, but there’s more to it than cranking up the specifications. Nvidia has leapt from the “GTX” to “RTX” brand name for a reason.

Ray tracing is that reason. But what is ray tracing, and how will it make your games look better?

Ray tracing does what it says on the tin

Graphics technology is usually hard to explain, but ray tracing is rather simple. It works a bit how it sounds. Ray tracing creates an image by tracing the path of simulated light. Or, rather, millions of simulated lights. The light bounces of objects as it moves and interacts with their properties. If it bounces from a glossy green surface, for instance, its hue may change.

That’s essentially how light works in real life. A particle of light springs from its point of origin and travels along until it interacts with an object, at which point its path is determined by that object’s properties. It might be absorbed by a dense, dark object, or almost entirely reflected by a mirror.

Ray tracing’s fundamental similarity to real life makes it an extremely realistic 3D rendering technique. There’s just one problem: It’s hard to simulate. The world we see every day is made visible by millions upon millions of light particles bouncing about at, well, the speed of light. Simulating that isn’t easy, which is why modern real-time 3D graphics – including those used in 3D games – rarely use this technique. It’s typically reserved for movies and other pre-rendered graphics, where it’s possible to spend hours rendering just a single frame. Until now, that is.

Enter Nvidia

Graphics technology has improved, however, and Nvidia’s latest RTX 2000 series cards are the first to include hardware specifically built for ray tracing. The new Turning architecture uses the company’s new Tensor Cores to handle the technique in real time. Nvidia had a few specific demos to show at its press conference including Battlefield V, Shadow of the Tomb Raider, and Metro Exodus.

The Shadow of the Tomb Raider demo is probably the best demonstration because its slow and simple, giving you a chance to look closely at the details.

What’s interesting in the Tomb Raider demo is not just the light, but the shadow. You’ll notice that shadows are highly refined, extremely accurate, and offer excellent contrast. The dancers swaying in front of the neon lights, for example, are virtually silhouettes. Achieving that look without ray tracing is extraordinarily hard. Developers can only “fake” it through careful, controlled use of preset light sources. That takes a lot of time and effort – and even then, the result isn’t quite right.

The children with the firecrackers also offer a wonderful demonstration. You’ll notice how the shadows of people nearby flicker realistically as the firecrackers crackle and waver. This, too, is a look that’s almost impossible to achieve using current real-time 3D rendering techniques. The simulation of light simply isn’t complex enough to achieve it.

While the Tomb Raider demo focuses on shadows, the demo Battlefield V focuses more on reflections. You see the reflection of troops in water, the reflection of terrain on airplanes, and the reflection of explosions across a car’s paint. It’s of course possible to show reflections in modern 3D engines, but not at the level of detail shown in the Battlefield V demo. Gamers are accustomed to seeing mottled, dull, or pixelated reflections in even the most advanced 3D games. Ray tracing can eliminate those problems.

In addition, these reflections can now be seen even when the source of the reflection isn’t on screen. As demonstrated in the Battlefield V demo, something like an explosion seen in the reflection of an eye had to be simulated before — and remained static. Now environments feel more alive, which add a lot of realism in a game like Battlefield V where chaotic action is supposed to surround you in every direction.

How can you see ray tracing at home?

Nvidia’s new hardware is meant to accelerate ray tracing, but it’s not the first case of the technique being used on consumer-level hardware. A few games have tried to use ray tracing in the past. In 2008, researchers at Intel managed to create a version of Quake Wars that used real-time ray tracing. It was just an experiment, however, and the game only ran at 20 to 35 frames per second on an Intel quad-socket (yes, as in four processors) rig.

The new RTX 2000 series cards will finally let you see ray tracing at home, but less than two dozen games currently plan support. These include those previously mentioned and a few other anticipated titles, like Mechwarrior 5: Mercenaries. Still, the list is rather slim, and we expect that developers will be slow to jump on board. None of those are available at launch with the RTX 2080 and 2080 Ti.

If you want to see ray tracing at home, though, it’s not that difficult. Just buy one of Nvidia’s expensive new video cards and wait for a compatible game to come out. After that, it (should be) as simple as flipping a switch in the game’s menu.

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