author: Ramzes
Is GeForce RTX Worth It? Games with the Best Ray Tracing
Since the introduction of GeForce RTX 2080, we haven't seen many ray tracing games. However, the release of RTX 3080 and its support for this technology in the PS5 and Xbox Series X means we're right at the threshold of new era of graphics.
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Minecraft RTX – cuboid revolution
The fact that ray tracing comes to Minecraft was quite a surprise, and the addition of ray tracing here showed how important realistic lighting is in computer games. So far, the artists have done it manually (or not at all, like originally in Minecraft without modified shader), but even PBR (physically-based rendering) doesn't come close to ray tracing.
Each tonal transition in a room is visible at a glance. Sunlight falls through the window and spills all over the room, giving the effect of both hard light on the section of a surface, on which rays fall directly, and soft, scattered light, indirectly illuminating the whole room. The limit here is, of course, performance, so proper adjustment of the number of rays is crucial to maintaining high framerate. A substitute of what ray tracking does here is available in Assassin's Creed: Unity, which uses PBR and pre-calculated light scenes.
Using the real properties of materials in Minecraft, we can see one more thing. Namely, interaction of objects with ambient light. When placing a block, which is metal or glass, it will automatically be adequately illuminated and shaded, and reflections as well as refractions of its color will appear on the surfaces next to it. Hence, you don't have to use pre-calculated scenarios, as rays tracking will do it for you – only in shorter time, and also more precisely. This is also the main reason why light has not previously interacted with objects in the game.
Quake 2 RTX
Quake 2 is a great example of how demanding ray tracing really is. The game was originally released in 1997, which makes it older than many people reading this article. This was the time when the first signs of hardware acceleration used by GPUs were popularized. The RTX version does not get rid of rasterizing in its entirety, because some effects are still the same, but what we can see on the screen is ray tracking by all intents and purposes.
Of course, the game itself won't look good, because it tried to preserve the textures from the original, but the greatest dissonance can be observed in the case of lighting and shading. Differences become much more pronounced here: from a dark game that's uniformly lighted in every room, this becomes a production that allows every nuance of ray tracking to shine with full glory.
The best example of that is firing rockets. Immediately after the shot is fired, we can see soft shadows of the projectile on the walls, and the illuminated changes color to match the propellant. Finally, the explosion causes a fireball whose light falls on every possible surface around. If you do it near water, you will be able to see a precise reflection on the surface. Such an effect is impossible to achieve without ray tracing, and it adds significant realism.
Control – created for ray tracing
In my opinion, the biggest premiere in terms of introducing ray tracing into games was Control. Not because it's almost entirely rendered using path tracing, but because it is the first AAA game to simulate a realistic visual setting with so many RT effects. Released in 2019, the production boasts many effects calculated on RTX cards from Nvidia. The most important effect is of course reflective ray tracing, which makes the game much more realistic.
From now on, you can see your character and surroundings in window reflections, which in the case of even SSR (screen-space reflections) was either impossible, or very inaccurate. Additionally, the reflections on each surface were treated in the same way. However, this doesn't mean that every surface becomes a mirror. Ray tracing reflections interact differently with different materials depending on their properties, so the reflections on polished wood will be different from reflections in glass.
But that's not all. Tracing indirect scattered light adds natural softness to scenes illuminated by global lighting, which we can see in Metro: Exodus, Minecraft and Quake 2 RTX. Although the regular global lighting rasterization looks really good in Control, it isn't able to attain such fidelity as RTX. This is especially visible when casting reflected light, whose color corresponds to the color of objects reflecting this light – this effect is absent in case of rasterization.
Ray tracing of contact shadows adds shadows cast by smaller objects, in places where standard maps cannot generate such details. It's a small difference, because usually while playing, we don't notice something like shadows cast by door handles. However, the effect is available and tops off the whole scene. The last effect is ray tracing of particle objects. Control is known for physics that cast particles around every room. The impression is great, but without ray tracing, they do not generate reflections on surfaces.
Metro Exodus
The latest entry in Metro series has some of the ray tracking effects. The creators decided to add global lighting, which is significantly better than what we usually see on screens in games using pure rasterization. Despite the fact that the effect is not so noticeable in full sun or generally in open areas, where a low number of objects effectively masks the imperfections of the previously calculated light scenes, the effect is striking in any room with penetrating sun or moon light.
Despite the fact that AC: Unity is already 6 years old, it still looks very good in this respect, often outshining new productions. But even that didn't get close to what ray tracking in Metro: Exodus looks like. The example above shows how much indirect lighting obtained by means of ray tracing differs from traditional rasterization and artificial cube maps arrangement.
Not only do we have the right color reflecting on the wooden floor, but realistically shaded objects illuminated by indirect light as well. In case of rasterization, each object on the scene is lifeless, monotonous, with the same lighting and shading. After turning on RTX we can additionally observe how a dynamic object (in this case – a character) starts to cast its shadow and shadow itself at the same time, which is completely absent in case of rasterization.