What is ray tracing and how does it work?

Ray tracing is a well-established method of rendering 3D graphics that emulates the behavior of light. It has been used in various fields like film, animation, and 3D modeling, particularly when realistic rendering is prioritized over system resources and rendering time. The exploration of ray tracing began as early as the late 1960s, with Ivan Sutherland being one of its pioneers through the development of the Sketchpad application for simulating light reflections on surfaces. However, due to the complexity and cost associated with ray tracing, game engines have predominantly relied on rasterization and direct lighting.

Ray tracing technology simulates the behavior of light in a virtual scene by generating rays from the camera's viewpoint and tracing them through the scene. The objects in the scene are categorized based on their ability to absorb, transmit, or reflect light. The process begins with a virtual beam shooting from the player's eyes and interacting with all the physical objects in the scene, including NPCs, buildings, vehicles, furniture, and more. When a ray intersects with an object, the point of intersection is calculated, providing information about the color and brightness needed to create the final image. In essence, ray tracing attempts to replicate how light is perceived by the human eye.


Ray tracing technology enables the reflection, absorption, and refraction of light as it interacts with the surfaces of objects, closely resembling real-world light behavior. It can also generate realistic shadows based on the physical properties of objects and the positioning of light sources. These capabilities allow for the creation of intricate effects such as rain in sunlight, neon-lit fog in games like Cyberpunk 2077, or reflections of characters in passing cars, as seen in Spider-Man. As a result, games that may not have been initially designed to prioritize visual beauty can be transformed with realistic lighting, shadows, and reflections. Take, for example, the clips showcasing the application of ray tracing to Minecraft and Quake 2, both of which originally presented a simplistic, cave-like aesthetic but gained new vibrancy through enhanced lighting effects.

Difference in tracing between previous and current generations of graphics cards

Photo from the presentation of NVIDIA Ampere video cards.

Ray tracing is a computationally demanding process that places a significant load on graphics cards. Graphics card manufacturers have approached this challenge in different ways. AMD's Radeon cards typically focus on software-based solutions that aim to provide a cost-effective option for the majority of gamers. On the other hand, NVIDIA has chosen a high-quality approach by incorporating dedicated ray tracing cores in their Turing, Ampere, and Ada Lovelace series of graphics cards. These specialized cores are specifically designed to handle the complex calculations involved in ray tracing, resulting in improved performance and rendering quality.

Early implementations of ray tracing technology faced mixed reactions. The high cost of video cards in 2019 made it difficult for many gamers to adopt the new technology, resulting in limited accessibility. Game developers also had varying levels of understanding and implementation, sometimes incorporating ray tracing features primarily for visual appeal, similar to the way 3D cinema gained popularity after the success of Avatar. However, certain games like Cyberpunk 2077, Battlefield V, and Metro Exodus showcased noticeable improvements in visual quality after the addition of ray tracing. On the other hand, games like Call of Duty: Modern Warfare and Shadow of the Tomb Raider struggled with increased system load and had limited graphical enhancements despite the added strain on video cards.

The implementation of ray tracing in the GeForce RTX 30XX series of video cards involves several technical nuances.

In the fall of 2020, NVIDIA unveiled the next generation of GeForce Ampere video cards to showcase the long-term commitment to ray tracing technology. The new cards featured an increased number of RT cores specifically designed for ray tracing, delivering improved efficiency and performance. NVIDIA also introduced new algorithms for simulating and optimizing lighting, including advancements in secondary ray tracing. This method greatly enhanced the handling of global and local illumination, resulting in more accurate dynamic shadows and improved surface material modeling within in-game scenes. These developments reinforced NVIDIA's dedication to advancing the capabilities and realism of ray tracing technology.

The introduction of SCG (Simultaneous Computer and Graphics) technology enabled the RTX 30XX graphics cards to efficiently distribute graphics and computing work among different cores, allowing them to operate independently. This advancement improved overall performance and efficiency. Additionally, NVIDIA's engineers made significant progress with DLSS 2.0, an artificial scaling technology that reduced the computational load of ray tracing by using neural networks to render missed frames. The combination of these advancements resulted in a more visually stunning and efficient ray tracing experience compared to previous iterations. However, these developments were just the beginning, setting the stage for even more impressive advancements to come.

Performance Gaming Laptops

What is path tracing? (technical details)

Visual difference between path tracing, ray tracing and standard rasterization. Source: NVIDIA.

Conventional light ray simulation, as described earlier, traces light rays, their intersections with objects in the scene and interaction with light sources. Path tracing, on the other hand, is a more powerful and flexible technique that simulates the physical behavior of light as closely as possible to the real world. If ordinary ray tracing was called by many experts a staging post, path tracing looks like the final destination of a journey.

In contrast to traditional lighting simulation, path tracing follows the complete path of each light ray as it interacts with objects and returns to the light source. It considers all forms of lighting, including direct, reflected and diffuse light energy, resulting in more realistic and intricate lighting effects. This includes the accurate representation of global illumination, which takes into account multiple light sources. While path tracing shares similarities with ray tracing, there are numerous technical details that distinguish it, leading to distinct and noticeable differences in the final rendering.

The official trailer with the presentation of Ray Tracing:Overdrive Mode in Cyberpunk 2077:

The first significant evaluation of path tracing in games was conducted by Digital Foundry, who tested Cyberpunk 2077 using the RT: Overdrive mode. Through videos and screenshots, they demonstrated substantial differences in various scenes compared to traditional lighting and basic light simulation. For instance, in a closed garage without any light sources, visibility is severely limited without a flashlight. Characters appear more realistic and lack the gray aura often associated with basic lighting. Stepping from darkness into bright light can be overwhelming, as the sun's brightness feels blinding, resembling a scorching July day.

Video with a detailed comparison of conventional ray tracing and path tracing from Digital Foundry:

It should be noted that the difference in graphics is primarily attributed to the original implementation of a hybrid lighting system in Cyberpunk 2077, which combined elements of both rasterization and ray tracing. CDPR developers faced limitations with the engine, allowing only up to 10 light sources with shadows per scene. However, with path tracing, they were able to overcome these limitations and achieve a more comprehensive lighting system. Path tracing enabled the casting of shadows by any light source, and surfaces were able to accurately reflect or absorb light. Moreover, the implementation considered not only static light sources but also dynamic ones, such as car headlights or a shaking flashlight held by the player.

How many resources does path tracing consume and what kind of hardware do you need?

The demanding nature of full 4K path tracing without DLSS can put a significant strain on even high-end graphics cards like the flagship GeForce RTX 4090.

Based on tests of the RT: Overdrive mode, which simulates path tracing in Cyberpunk 2077, it is evident that the technology puts a significant strain on modern graphics cards. Even powerful options like the GeForce RTX 4090 with its 24 GB of video memory struggle to handle the workload, resulting in significantly reduced frame rates. Averaging around 18 — 20 FPS is a clear indication of the computational demands involved. To address this, CDPR developers emphasized the need to use DLSS 3.0, an artificial frame generation technology, in conjunction with RT: Overdrive to alleviate the heavy load and improve performance.

CDPR noted that DLSS plays a critical role in creating a realistic image. With the help of DLSS neural networks, finishing frames for rendering of which there were not enough resources of the video core, transferring the load to the tensor cores allocated for this task. Also, DLSS 3 frame generation allows the user to improve the quality of the original image before scaling. During the Cyberpunk 2077 test, with DLSS 3 turned on in "Performance" mode, the average frame rate increased from an unpleasant 35 — 40 FPS to a more than comfortable 90 FPS.

NVIDIA GeForce RTX 4090 graphics cards

When will path tracing become accessible to the general public?

Comparison of two frames with different tracing modes.

The technology showcased in Cyberpunk 2077 should be seen as a demo — a visually stunning and promising display that, while impressive, can be buggy and demanding on system resources. NVIDIA is actively collaborating with major AAA studios to refine and optimize the technology. As an example, the NVIDIA RTX Remix (https://www.nvidia.com/ru-ru/geforce/rtx-remix/) open source feature has already enabled modders to implement path tracing in games like Half-Life 2. The modding process was relatively straightforward, as RTX Remix handles lighting placement and automates several other tasks. The release of RTX Remix is expected to pave the way for similar mods in many other games in the near future.