RT (Ray tracing)

Ray tracing is a rendering technique used in computer graphics to simulate the behavior of light in a virtual scene. It aims to produce highly realistic and physically accurate images by simulating the path of individual rays of light as they interact with objects and surfaces in the scene.

In traditional rendering techniques, such as rasterization, images are created by determining the color of pixels based on their position, surface properties, and lighting conditions. While rasterization is fast and efficient for real-time rendering, it often produces less realistic results, especially in terms of lighting and reflections.

Ray tracing, on the other hand, takes a different approach. It models the behavior of light by tracing the path of rays as they are emitted from a virtual camera, interact with objects in the scene, and reach the virtual light sources. The process involves several stages:

1. Ray Generation: The first step is to generate primary rays, also known as eye rays, from the virtual camera. These rays originate from the camera's position and pass through each pixel on the image plane.
2. Ray Intersection: The generated rays are then tested for intersection with objects in the scene. This is done by comparing the rays against the geometry of the objects, typically represented as triangles or other primitives. The goal is to determine which objects, if any, the rays intersect with.
3. Shading: Once an intersection is found, the shading process begins. The properties of the intersected surface, such as its color, reflectivity, transparency, and roughness, are evaluated and used to calculate the contribution of various light sources. This involves simulating the interaction of light with the surface based on the material properties and the lighting model being used.
4. Secondary Rays: In addition to primary rays, secondary rays are often generated during the shading process. These rays are used to simulate effects like reflections and refractions. For example, when a primary ray intersects a reflective surface, a secondary ray is spawned in the direction of the reflected light. Likewise, when a primary ray intersects a transparent object, a refracted ray is generated.
5. Recursive Tracing: The process of generating secondary rays and tracing their paths can be repeated recursively to simulate complex light interactions. For example, when a reflected ray hits another surface, it can generate more secondary rays, leading to multiple levels of reflection.
6. Light Sources: Rays that reach light sources in the scene contribute to the final color of the pixels. The contribution is determined by factors like the intensity and color of the light sources, as well as the properties of the surfaces the rays intersected with.
7. Global Illumination: Ray tracing can also simulate global illumination effects, such as indirect lighting and soft shadows. Indirect lighting refers to the light that bounces off surfaces and illuminates other objects in the scene. Soft shadows occur when light rays are partially blocked by objects, leading to gradual transitions between illuminated and shadowed areas.
8. Antialiasing: Ray tracing can produce sharp and accurate results, but it can also introduce aliasing artifacts due to the discrete nature of pixels. To mitigate this, techniques like supersampling or filtering can be applied to smooth out the jagged edges and improve the overall image quality.

Ray tracing can be computationally expensive since it involves simulating the path of individual rays and their interactions with objects. However, with advancements in hardware and algorithms, real-time ray tracing has become increasingly feasible, enabling more immersive and visually stunning graphics in video games, virtual reality, and other applications.