What is ray tracing?

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Ray tracing is one of the most talked-about graphics technologies in recent years. It promises photorealistic rendering, but also demands a great deal from GPU resources. Here is everything you need to understand about this technique and its concrete impact in games.

What is ray tracing?

Ray tracing is a rendering technique that simulates the real physical behaviour of light. Rather than calculating lighting in an approximate way as traditional rasterisation does, ray tracing traces the path of light rays pixel by pixel, simulating their reflections, refractions and absorptions throughout the scene.

In practice: the graphics engine fires rays from the camera towards each pixel of the image, calculates which objects these rays collide with, then determines how light reflects or refracts from those contact points to compute the final colour of each pixel.

Ray tracing vs rasterisation: what is the difference?

Until the arrival of real-time ray tracing, all video games used (and still mostly use) rasterisation — a technique that projects 3D polygons onto a 2D screen and simulates lighting with approximations and visual tricks (shadow maps, screen-space reflections, ambient occlusion…).

What ray tracing improves visually

Ray tracing has a particularly noticeable visual impact on several aspects of rendering:

• Reflections: reflective surfaces (water, polished metal, glass) display true reflections of surrounding objects — even those off-screen
• Soft shadows: projected shadows are naturally soft at their edges, as in reality, rather than pixelated and hard
• Global illumination: light genuinely bounces from surface to surface, lighting shadowed areas indirectly
• Ambient occlusion: corners, crevices and spaces between objects are naturally darkened according to their exposure to light
• Caustics: light patterns created by the refraction of light through water or glass are rendered with accuracy

Impact on performance

Ray tracing is extremely demanding computationally. Enabling ray tracing in a game can reduce FPS by 30 to 60% compared to rasterisation alone, depending on the implementation level and GPU used.

This is why NVIDIA developed RT Cores in its RTX GPUs (since the RTX 2000 series), and AMD introduced Ray Accelerators in its RDNA2+ GPUs. These dedicated hardware units accelerate ray tracing calculations without going through traditional shaders, making the technology usable in real time — provided it is combined with upscaling technologies.

Ray tracing and DLSS / FSR: an essential pairing

To compensate for the FPS loss caused by ray tracing, developers almost always pair it with upscaling technologies:

• DLSS 3/4 (NVIDIA): uses artificial intelligence to reconstruct a high-resolution image from a lower-resolution rendered image, recovering a large portion of the lost FPS
• FSR 3 (AMD): a similar open-source solution compatible with most GPUs, less effective than DLSS but accessible on a wider range of cards
• XeSS (Intel): Intel's upscaling solution available on Arc GPUs and partially on NVIDIA and AMD

Good to know: in 2026, most players who enable ray tracing do so with DLSS or FSR simultaneously active. Without upscaling, ultra ray tracing at 4K remains out of reach even on the most powerful GPUs such as the RTX 5090 or RX 9900 XTX at playable framerates.

Partial ray tracing vs full ray tracing (path tracing)

There are different levels of ray tracing implementation in games:

• Partial ray tracing: only certain effects (shadows, reflections or global illumination) use ray tracing, with the rest remaining in rasterisation. This is the case for the majority of games today
• Path tracing: an advanced form of ray tracing that simulates all aspects of lighting through ray casting. Alan Wake 2, Cyberpunk 2077 (Overdrive mode) and Indiana Jones and the Great Circle are among the first games to offer full real-time path tracing

Path tracing produces the most photorealistic images ever seen in real time, but it is also the most demanding — it requires a recent high-end GPU and DLSS/FSR to remain playable.

Good to know: if you mainly play competitive games (CS2, Valorant, Apex Legends), disable ray tracing. These games do not benefit visually from it in any significant way, and the extra FPS gained without ray tracing are far more valuable to your performance than the visual realism it provides.