What’s ray tracing? Here’s everything you need to know

Ah, ray tracing. Although it’s been around for a long time in the film industry, it’s still a rather perplexing term, especially where video games are concerned. Essentially, it’s a technique that makes light behave in a realistic way. The idea is to make games more realistic and immersive. Wouldn’t you be spellbound by the light bouncing off of objects in a natural way? The indistinguishable line between reality and fantasy is no doubt appealing.

If you’d like to better understand ray tracing and its impact on games and a computer system, at a high level rather than descending too deeply into tech gobbledygook, keep on reading.

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What is ray tracing?

Imagine you’re playing a PC game with the graphics cranked all the way up. Maybe it’s an open-world game like Cyberpunk 2077, where there are loads of objects and textures. As you duck into an alleyway to hide from your enemies and take a breather, you notice the pinkish light from a neon sign bouncing off of the wet pavement. That’s ray tracing. Your graphics card renders these hyper-realistic effects in real-time, which makes for a more dynamic environment. That means shadows will move according to the sun’s position and look softer. But let’s dive a bit deeper, shall we?

Ray tracing works by using an algorithm that tracks beams of light. When the light hits an object or surface, the algorithm calculates the way it interacts with it, and with the way it interacts with other rays of light bouncing off different surfaces of their own. The idea is to mimic how the human eye processes light and shadows in real-time. That’s what makes it so realistic-looking. For a much wonkier dive into how ray tracing works, especially on Nvidia graphics cards, read the “RT Core” section of our Nvidia Turing GPU deep dive (ray tracing debuted in mainstream graphics cards on the Turing-powered GeForce RTX 20-series), or our original coverage of Microsoft’s DirectX Raytracing API, which serves as the backbone for ray tracing on Windows systems.

While ray tracing produces impressive results, it can be quite taxing on your GPU, as keeping track of all those light rays requires a massive amount of power. It’s also computationally expensive to trace all those rays. That’s why most video games typically use traditional rasterization instead. It’s much speedier and it doesn’t burn up as many resources. Even games that support ray tracing tend to rely on rasterization for the vast majority of visuals, deploying the cutting-edge lighting effects for only a few key features.

Rasterization

Rasterization is how most video games are traditionally rendered. Simply put, it’s the process in which the GPU assembles a 3D scene. I like to think of the GPU as the sculptor and the polygons as the clay. Once the scene is set, these polygons get transformed into 2D pixels and then gets fine-tuned with shading, lighting, colors, and textures. One limitation to rasterization is inaccurate lighting effects. This technique can’t quite track light and calculate how it should hit virtual objects like ray tracing does, forcing developers to put a lot of work into “faking” lighting and its associated effects instead.

That’s where ray tracing comes in, in supported games—though your frame rates still plummet when even limited ray tracing features kick into action. That’s why the rise of ray tracing has come hand-in-hand with new image upsampling technologies that help reduce the load on your graphics card, boosting performance back up.

DLSS and FSR

DLSS is the acronym for Nvidia’s Deep Learning Super Sampling. This technology works by rendering a video game at a lower resolution and then upscales those frames to your chosen resolution, using artificial intelligence and temporal data from multiple frames to help fill in the blanks. The idea is to make a game look as sharp as possible without sacrificing performance. So, what does this technology have to do with ray tracing? Well, it’s supposed to make ray tracing work faster. Because ray tracing puts a lot of stress on your GPU, most games plummet below the respectable 60 frames-per-second. DLSS helps improve ray tracing by taking some stress off of the GPU.

FSR stands for FidelityFX Super Resolution and is AMD’s upscaling solution. Similar to Nvidia’s DLSS, FSR lowers your game’s resolution and then uses a “spatial” upscaling technique to show your game at your full chosen resolution. In other words, your game will look like it’s running at a higher higher resolution than it actually is. FSR is a bit different than DLSS, though. For one, it works across different generations of GPUs, including Nvidia’s GeForce cards. The source code is also free for developers, which is pretty darn rad. FSR’s spatial upscaling delivers a more noticeable hit to visual quality than DLSS if you crank them to their faster Performance options, but both work very well when set to Quality or Ultra Quality presets, especially on pixel-packed 1440p or 4K displays.

The proof is in the pudding

If you’d like to see what full-blown ray tracing looks like in action in a fully path-traced game, check out the stream above. In the video, the team at PCWorld explores Minecraft with ray tracing enabled. As you can see, there’s a huge difference in image quality. The surface of the water is reflective and glass-like, and the log cabins cast realistic-looking shadows on the ground. When Adam Patrick Murray, PCWorld’s video director, looks up at the sky while underwater at the 44:28 mark, you almost have to squint because the mid-day sun is so bright. It’s just beaming straight into the water. This technology is lovely and immersive, sure, but it comes at a cost.

Ray tracing has a huge impact on performance, as it requires more processing power from your system. You’ll definitely see those frame rates plummet, which is a real bummer. This will happen even with the most powerful GPUs. There aren’t many games that support ray tracing, either, and the ones that do only tend to support ray tracing for a few effects—like reflections or shadows—rather than being fully path-traced, like the Minecraft video above. That said, if you really care about aesthetics and have the right graphics card, you should definitely give it a try. The realistic effects look truly incredible when it’s done well.