We see the world around us when light bounces off objects and into our eyes.
Shadows are produced when light is blocked and refraction occurs when light passes from one medium to another, like from air to glass.
Ray tracing, often dubbed the holy grail of computer graphics, tries to mimic these natural phenomena by simulating the behaviour of light rays to create 3D objects. With ray tracing, rendered images can be extremely photo-realistic.
It is not a new technology – chances are, you have seen its results in the form of computergenerated imagery (CGI) in movies.
But ray tracing comes at a price. CGI scenes can take weeks, even months, to produce using render farms consisting of many powerful computers.
While this approach is feasible for movies, ray tracing is not suitable for video game graphics because the images have to be rendered in real time.
Instead, the computing industry found another solution – rasterisation – which uses virtual triangles, called polygons, to create 3D objects.
These polygons are mapped into a 2D plane, along with key information such as the colour and texture to be displayed on a computer screen.
Rasterisation plays to the strengths of computers, which are quick to perform identical tasks. But it also involves a certain amount of guesswork. And while it is possible to use rasterisation to render accurate and realistic images, the computation cost increases too.
This led Nvidia to take a hybrid approach with its latest generation of graphics cards. The new RTX 20 Series graphics cards can use both rasterisation and ray tracing techniques.
It is up to developers to decide how and when to use each method.
EARLY RAY TRACING IMPRESSIONS
So far, just a handful of released games use ray tracing. None of them relies completely on ray tracing because of the computational cost. Battlefield V, for instance, uses ray tracing to create more accurate real-time reflections, while Metro Exodus uses it to produce more realistic lighting in the game.
As you might imagine, the impact of ray tracing is limited in Battlefield V because it is an action-packed shooting game, not a tour in a house of mirrors.
I had to examine closely to notice ray tracing at work. For instance, the reflections in a puddle on a war-torn street show smoke wafting over the puddle with ray tracing enabled. It is clearly more realistic than the vague shadows passing over the puddle without ray tracing.
On the other hand, ray tracing is far more evident with the firstperson shooting game Metro Exodus.
Shadows and enclosed areas with few light sources appear darker with more depth.
With ray tracing, the weapon in my hand is a dark shadowed outline while turning off ray tracing seems to increase the brightness and lets me see more of the weapon.
In other words, ray tracing gives developers the chance to render a scene more accurately than before. The corner of a room, for instance, may actually be dimmer than what we expect.
Now, whether it is better, from an artistic point of view, is subjective – after all, movie-makers do not always strive for photo-realism in their films.
From what I can tell, ray tracing does not have any impact on game play, especially given its limited implementation in games at the moment. But enabling the feature takes a toll on the game’s performance.
In Metro Exodus, with ray tracing set to High, a tier below the maximum Ultra setting, the game ran at around 86 frames per second (fps) at 1,920 x 1,080 pixels on the Asus ROG Zephyrus GX701 with its Nvidia GeForce RTX 2080 (Max-Q) graphics chip.
Turn ray tracing off and the performance went up significantly to reach an average of 121fps.
A similar dip in performance was noticed in Battlefield V, with frame rates falling from 110fps to 63fps once ray tracing was enabled.
While these frame rates are high enough to ensure a smooth gaming experience on the GX701 even with ray tracing enabled, gaming computers with less powerful hardware may not fare as well.
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