The Evolution of Graphics in Games: Rasterization, Ray Tracing, and Path Tracing

The world of graphics in video games has come a long way. From the traditional technique of rasterization to the emergence of ray tracing, and now the more advanced path tracing, developers continuously strive to deliver more realistic visuals. In this article, we explore the main differences between rasterization, ray tracing, and path tracing, and shed light on the benefits of path tracing in game graphics.

The Basics: Rasterization

Traditionally, developers utilized a technique called rasterization to render graphics in games. Rasterization involves transforming mathematical vector shapes into pixels, allowing them to be displayed on computer monitors or pixel-based displays. While rasterization was effective in approximating light behavior in games using pre-rendered lighting with static light sources, its limitations became evident as the demand for photorealistic graphics grew.

The Emergence of Ray Tracing

Ray tracing, unlike rasterization, aims to simulate light behavior in reality for every frame of the game or application. As light interacts with various objects, it can reflect, refract, or get absorbed. Ray tracing calculates the same behavior for each individual pixel, resulting in millions of simulated rays per frame. This computationally demanding technique became accessible to gamers with the advancement of technology.

Ray tracing itself is not a new concept but has been used by film studios since the 1970s. However, real-time ray tracing in games is a different challenge altogether. It requires executing these complex calculations in a dynamically changing environment for every single frame. To mitigate the computational load, most games with ray tracing combine it with rasterization, leveraging its hardware acceleration for certain elements like reflections and shadows.

The Introduction of Path Tracing

Now, let’s dive into path tracing. In essence, path tracing is a modified version of ray tracing. Instead of tracing the path of every individual light ray, whether primary or secondary, path tracing calculates only the most probable path light would take as it traverses the scene. Developed in the 1980s, path tracing involves more complex mathematics, involving multiple rays per pixel, but ultimately resulting in lower hardware load, i.e., your GPU.

Path tracing is an approximation of ray tracing using Monte Carlo simulations – probability models that help predict the most likely outcomes in situations where precise prediction is impossible. It produces more realistic lighting in games by sampling a greater number of data points. Unlike ray tracing, which sends out multiple light rays for each pixel, path tracing samples only a subset of them to achieve the final result. This algorithm, aided by Nvidia DLSS denoising, allows for better-defined shadows, reflections, and global illumination.

The Advantages of Path Tracing

So, if path tracing is just an approximation of ray tracing, why is it considered better? Shouldn’t the result be worse than ray tracing?

Not at all. The path tracing vs. ray tracing debate is more nuanced. Path tracing, also sometimes referred to as full ray tracing, actually produces more realistic lighting in games. Recent titles like Cyberpunk 2077 and Alan Wake 2 have showcased what full-fledged ray tracing, with the help of path tracing, can achieve.

Path tracing has even been implemented in older games like Quake 2, Portal, The Elder Scrolls V: Skyrim, and Half-Life, transforming them from outdated graphics to technological showcases.

Path tracing’s ability to produce more realistic lighting stems from the increased sample data it can access. Unlike ray tracing, which only samples a subset of the available light rays, path tracing sends out multiple light rays for each pixel, resulting in better-defined shadows, reflections, and global illumination.

Technically speaking, path tracing is also easier to handle on GPUs. Despite the more complex calculations, denoising, and AI-related tricks involved in path tracing, it theoretically proves to be less demanding on the GPU.

The Future of Graphics in Gaming

Games developed from the ground up using path tracing will benefit the most from the reduced hardware load. However, this practice is still rare today. Path tracing is gradually being introduced to different games as updates, often years after the initial release.

Even “fully ray traced games” like Alan Wake 2, which Nvidia touts, do not extensively utilize path tracing. Nevertheless, these games still offer breathtaking visuals, even on the PS5.

Currently, running such titles at playable framerates, even with the most powerful GPUs, remains challenging. Nvidia’s upcoming RTX 40 series cards will have to leverage artificial intelligence features to render these games at lower resolutions and scale them for acceptable results.

But in a few years, thanks to advancements in AI technology, implementing path tracing will become significantly easier on GPUs available to all players.

FAQs

1. What are the main differences between rasterization, ray tracing, and path tracing?

Rasterization is the traditional technique for rendering graphics in games, transforming mathematical vectors into pixels. Ray tracing simulates light behavior in reality and calculates the light paths for each pixel. Path tracing calculates the most probable light path for each pixel.

2. How does ray tracing work?

Ray tracing calculates the behavior of light rays in a game scene, considering reflections, refractions, and light absorption by objects. It analyzes each light ray for each pixel, requiring extensive computational power.

3. How does path tracing work?

Path tracing calculates the most likely light path that light would take as it traverses the scene. It employs multiple light rays per pixel, but sampling is applied to reduce the computational load.

4. What are the advantages of path tracing?

Path tracing produces more realistic lighting with higher sample data. It can provide better-defined shadows, reflections, and global illumination. Technically speaking, path tracing is less demanding on the GPU compared to ray tracing.

5. Is path tracing used in games?

Path tracing is being introduced to some games as updates, but it is typically practiced years after the initial game release. Newer games like Cyberpunk 2077 and Alan Wake 2 employ path tracing to achieve more realistic graphics.

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