How does ray tracing work?

05 Tem 16:33

The working principle is actually based on the direct mathematical modeling of how light behaves in nature. That is, when a light ray hits objects, you calculate what happens using physical laws (Fresnel equations, Snell's law, etc.). At the basic step, you send a ray for each pixel and recursively track its interactions with surfaces—reflected, refracted, scattered rays—to obtain the final lighting result. In the past, this was only used in offline rendering because it required millions of calculations per pixel, but thanks to APIs like Vulkan/DXR, it's now used in real-time applications as well. The biggest trick for efficiency is producing optimal results with a reduced number of rays. For example, NVIDIA's RTX technology uses both hardware ray tracing cores and post-processing techniques like temporal reprojection to reduce computational load. If you try to render everything at once in first-generation ray tracing, FPS drops, but hybrid approaches like dynamic resolution scaling and using light probes for Global Illumination (GI) come into play. During my tests, I found that combining the advantages of rasterization (e.g., z-buffering) with ray tracing is the most logical way—handling parts that are hard to compute with direct ray tracing (like shadows and reflections) while rendering the rest with classic methods. When it comes to comparing rasterization vs. ray tracing... In rasterization, you quickly render 3D object surfaces by projecting them onto a 2D screen. The advantage is that it can deliver very high FPS, like 120+ FPS in 4K. The downside is that light isn't physically simulated correctly—shadows are harsh, and reflections are simplistic. Ray tracing does the opposite: it provides physically accurate light simulation, dynamic shadows, realistic reflections, and depth lighting. But it's expensive. Ultimately, each has its place: rasterization is the standard in real-time gaming, while ray tracing is used in scenes requiring enhanced lighting and graphics quality. Sometimes they even work together in hybrid renderers, like Lumen in Unreal Engine.

05 Tem 17:05

Ray tracing is based on the principle of creating a scene by completely tracing the paths of light rays, rather than directly simulating the physics of light. At its core is the "ray casting" algorithm: you send a ray from the camera and calculate which surface it hits and reflects off. During this reflection, you can also model how the surface material (e.g., mirror, matte, translucent) interacts with light. These rays are recursively traced as they reflect off other surfaces until they reach a light source. In real-time applications, of course, tracing millions of rays for every pixel isn’t feasible; that’s where NVIDIA’s "tracing instead of rendering" approach comes in: precomputed shadows, reflections, and lighting are optimized and only updated for dynamic elements, improving performance. The biggest advantage of ray tracing over rasterization is the more physically accurate simulation of lighting and reflections. For example, you can calculate how accurately an object interacts with a mirror in front of it, whereas rasterization typically relies on static light maps. From my experience using ray tracing in my own engine with the Vulkan API, the biggest challenge was performance optimization: dealing with stack limits for rays with high recursion depth or ensuring the GPU uses ray batching instead of optical ray marching. To optimize this, techniques like level of detail (LOD) methods—such as how rays are batched or which areas are prioritized for rendering—are essential. Finally, technologies like DLSS 3 have made real-time ray tracing more accessible by accelerating these calculations, at least on NVIDIA RTX cards.

05 Tem 17:28

Ray tracing involves shooting rays from each pixel into the scene and tracing them until they intersect with objects, enabling effects like natural lighting and reflections to be optimized from simple to complex through sequential trials—such as accelerating intersection tests with BVH (Bounding Volume Hierarchy).