What is ray tracing – understanding the next big leap in video game graphics

Ray tracing has been touted by many as the next big leap in video game graphics, it’s even been a big part of the next-generation PlayStation 5 and Xbox Series X consoles. But what is ray tracing and what benefits does it bring?

Before we answer the question of what is ray tracing, we need to discuss the two types of 3D video game lighting. The first of these is real-time dynamic lighting. This is lighting that’s simulated on the fly. Here, every highlight and shadow is calculated by your computer on the fly, in real-time.

How video game lighting works

The problem with this is that how light behaves is quite complex. A ray of light doesn’t just stop when it hits a surface. Rather it bounces around to other surfaces, affecting how they’re lit. Doing this can be computationally complex.

The usual form of real-time lighting used in games is called probe lighting. This uses static points, called “probes” to emit light on a scene. But this method doesn’t fully simulate how light rays bounce around a scene. It just highlights anything that’s directly within a probe’s radius. Anything outside of a probe’s direct line of sight isn’t affected. This is part of what lends video game graphics their, for lack of a better term, “gamey” look.

What is raytracing - half-life early probe lighting
Half-Life was one of the first games to use colored, real-time probe lighting

To get around the limitations of probe lighting, video game artists will often fake the lighting in a scene. This leads to the second kind of videogame lighting, static lighting. This is sometimes called “baked” lighting since the lighting is already “baked” into a scene.

Static lighting fakes most of a scene’s lighting and shadows through the use of texture maps and other effects. Here, artists will texture an environment in a way that already factors in where the light is coming from, with the artists manually tweaking the scene to make the lighting look more natural.

Most of the best-looking video games released in the past decade utilize a lot of well-done static lighting to look as good as they do. This includes big AAA games such as the Uncharted games, Call of Duty, Spider-man, Assassin’s Creed and others.

But static lighting still has its own drawbacks. It’s very labor-intensive for one, as each scene needs to be manually “lit” by artists. Also, it’s not well suited to handling moving lights. That tends to be given to real-time probe lighting instead. Then there’s the fact that it cannot do reflections. To these, artists need to resort to various tricks to create realistic looking reflections (sometimes even rendering whole “mirrored” scenes to create them).

What is raytracing- Spider-man faked reflections
Sucker Punch had to fake the reflections in those puddles.

If only there were a technology that could handle all these, in real-time.

What is ray tracing? Simulating how light works in real life

Ray tracing is actually one of the oldest methods of lighting 3D rendered graphics. The concept itself is pretty simple. The process just traces the path of every simulated ray of light and then render your lighting based on that path.

While the concept of ray tracing is simple enough, it is also quite computationally expensive, with each frame of animation of a ray-traced scene taking a while to render. As such, until recently, ray tracing has been the exclusive domain of film and television—speed isn’t an issue when your scene is being rendered to film in advance, the process of which can be offloaded to massive render farms, running dedicated equipment.

It was only recently that real-time raytracing has become a thing with the development of dedicated ray tracing hardware, first with Nvidia’s RTX line followed by AMD’s RDNA2 architecture, which powers the PlayStation 5 and Xbox Series X, on top of AMD’s own RX 6000 line of video cards.

What does this mean for games and gamers?

With real-time ray tracing, developers and artists can finally take advantage of this technology in their games.

That said, the benefits of real-time ray tracing may not be apparent at first to the average gamer. For some time, game developers and artists have been using static, baked in lighting to create the graphical fidelity enabled by ray tracing.

Perhaps real-time ray tracing’s greatest benefit can be for games that rely heavily on real-time lighting. That, as well as games that feature lots of colored lighting effects. One of the best examples of this is CD Projekt RED’s Cyberpunk 2077. Not only does this game feature a large open world with a day-night cycle, but it also features a ton of colorful light sources, especially at night. (Read: Cyberpunk 2077 hits 13 million in sales despite refunds)

In the screenshots of the game below, the version with ray tracing on clearly has better reflections.

Real-time ray tracing also provides benefits for developers. Having to bake in static lighting to make a scene look good requires extra work.

A good example of this would be 2017’s Horizon: Zero Dawn. To enable a day-night cycle, the artists at Guerilla Games had to create multiple static lighting setups for their game world. The end result was stunningly beautiful. That said, it still required a lot of effort that could have been saved had real-time ray tracing been available.

With real-time ray tracing, the idea is that developers will need to spend less time making their game look good. Developers can then spend this extra time on other parts of a game-in-development, hopefully resulting in a much better product at release.

Of course, for this to happen, more gamers need access to hardware capable of ray tracing. This is admittedly something of a challenge with the current supply issues for both ray tracing capable graphics cards and consoles. Hopefully, these companies can sort out their supply issues soon so that more people can experience this technology.

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Franz Co

managing editor | addicted to RGB | plays too many fighting games

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