December 31, 2024 Vivian Vu

Rasterization vs Ray Tracing vs Path Tracing: What is the difference?

Let’s delve into the distinctions between Rasterization, Ray Tracing, and Path Tracing to see what sets each apart. Understanding the differences between these techniques can help you appreciate how they transform digital models into stunning images

What is Rasterization?

Rasterization is a technique used in computer graphics to convert 3D objects into 2D images. Using rasterization, objects on the screen are formed from a mesh of virtual triangles or polygons that construct 3D models. In this mesh, the corners of each triangle, known as vertices, intersect with vertices from other triangles of various sizes and shapes. Each vertex holds significant information, including its spatial position, color, texture, and “normal” which indicates the orientation of the surface.

Computers then transform these 3D model triangles into pixels on a 2D screen. Each pixel initially receives a color value based on the data from the triangle vertices.

Further processing or “shading” adjusts the pixel color according to how lights in the scene interact with it and applies textures to achieve the final color for each pixel.

      • Pros 

Rasterization is incredibly fast, making it ideal for real-time applications such as video games and simulations

Suitable for real-time rendering.

      • Cons

Less accurate in handling lighting, shadows, and reflections. It can result in less realistic images, particularly in scenes with complex lighting.

May require more optimization and manual adjustments to maintain performance.

What is Ray Tracing?

Ray Tracing is a technique that creates an image by tracing the path of light through pixels on an image plane and simulating its effect when interacting with surrounding virtual objects. Ray means light ray, and Tracing means to track, to chase. In other words, Ray Tracing tracks the light absorbed, reflected, scattered and dispersed by each object in the environment, and it applies not only to a beam of light from the sun but to all different light sources.

For each pixel in the image, ray tracing starts by casting one or more rays from the camera’s viewpoint into the 3D scene. These rays are tracked as they bounce off surfaces (reflection), refract through transparent materials, or get absorbed by objects. The system calculates the color of the pixel based on the ray’s journey when a ray hits a light source or reaches a predetermined bounce limit.

      • Pros 

Highly realistic images with accurate lighting and shadows. Produces highly realistic images with natural-looking lighting and shadows, enhancing the visual quality of scenes.

Accurately simulates the way light interacts with objects, including reflections, refractions, and shadows.

      • Cons

It is computationally intensive and slow. It performs slower compared to rasterization, especially in scenes with complex lighting and many light sources.

Requires powerful hardware. Necessitates specialized GPUs with ray tracing capabilities (e.g., NVIDIA RTX series, AMD Radeon RX series) and strong CPUs. Limits accessibility to users with high-end hardware, potentially increasing the cost of entry for advanced graphics rendering.

What is Path Tracing?

Path tracing is a complex form of ray tracing, where the GPU calculates the paths of light rays and reflected beams to create more realistic lighting, shadows, and reflections. Path tracing is different from ray tracing, which tracks the path of light rays interacting with the environment in the virtual world. It can create advanced lighting effects but requires a lot of computer resources to execute. Path tracing is widely used in movies, video games, and for 3D rendering.

      • Pros 

Produces the most realistic images by accurately simulating global illumination.

Handles complex lighting scenarios, including caustics and diffuse interreflection.

      • Cons 

Very resource-intensive and time-consuming.

Requires significant computational power due to the extensive calculations involved in tracing multiple light paths.

The difference between Rasterization, Ray Tracing, and Path Tracing

Feature Rasterization Ray Tracing Path Tracing
Process Converts 3D objects into 2D images by projecting them onto the screen, filling in pixels row by row. Simulates the path of light rays as they travel through the scene, calculating intersections with objects to produce realistic lighting, shadows, and reflections. An extension of ray tracing that traces the path of light through many bounces, sampling random light paths to simulate global illumination.
Rays per pixel Typically one ray per pixel Multiple rays per pixel (hundreds or thousands)
Use case  Primarily used in real-time applications like video games. Used in high-realism scenarios, like film production and high-end visual effects. Produces extremely realistic images for high-end visual effects and photorealistic rendering.
Lightning and Shadows Limited accuracy Accurate lighting and reflections Simulates global illumination
Performance Extremely fast Requires powerful hardware Requires significant computational power
Applications Video games, simulations Film production, visual effects High-end visual effects, photorealistic rendering
Hardware Requirements Less demanding More demanding, can run on most modern GPUs More demanding, benefits greatly from high-end GPUs or render farms

Taking all these points into account, rasterization is equivalent to casting one set of rays from a single point that stops at the first thing they hit. Ray tracing takes this further, casting rays from many points in any direction. Path tracing simulates the true physics of light, which uses ray tracing as one component of a larger light simulation system. 

Rasterization is best for real-time applications where speed is crucial.

Ray Tracing is ideal for high-quality visualizations where accurate lighting and reflections are needed.

Path Tracing excels in producing photorealistic images with complex lighting but is the most computationally demanding.

The difference between Rasterization, Ray Tracing, and Path Tracing

Ray tracing and path tracing require high-end graphics cards because they involve complex calculations to simulate the behavior of light. Ray tracing traces the path of light rays as they interact with objects in a scene, calculating reflections, refractions, shadows, and more for each pixel. Path tracing, an extension of ray tracing, traces many rays per pixel to simulate light paths more accurately, resulting in even more complex calculations. These processes are computationally intensive and demand significant parallel processing power to achieve real-time performance, which high-end GPUs, like NVIDIA’s RTX series, provide. 

To meet these demanding requirements, iRender is the best choice. iRender offers high-performance GPU servers equipped with the latest NVIDIA RTX graphics cards, providing the necessary computational power for complex tasks like ray tracing and path tracing. By utilizing iRender, you can achieve optimal rendering performance without investing in high-end hardware, making it an excellent choice for professionals and enthusiasts seeking top-tier graphics solutions. You can see our packages with RTX 3090 and RTX 4090.

Below are our testing videos with RTX 4090, let’s watch!

Currently, iRender offers a special promotion for new users, a 100% bonus program for the first deposit within 24 hours of registration, making it an attractive option for those looking to optimize their rendering budget. Just register and get our best deal!

For more detailed information, please contact us via Live chat 24/7 or WhatsApp: +(84)915875500 or Email: [email protected]

References and image source: blogs.nvidia.com, egneva.com

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Vivian Vu

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