säteenseurantaperiaatteella

Säteenseurantaperiaatteella, which translates to "on the principle of ray tracing" in English, is a fundamental concept in computer graphics and optical simulation. It describes a rendering technique that simulates the physical behavior of light by tracing its path through a virtual scene. Instead of calculating how light from sources illuminates surfaces, ray tracing works backward from the camera, simulating the rays of light that would reach the viewpoint.

When a virtual camera renders an image, each pixel corresponds to a single ray originating from the camera's eye and passing through the pixel's position on the image plane. This primary ray then travels into the scene. If the ray intersects with an object, its properties are evaluated. The color and intensity of the pixel are determined by the material properties of the intersected object and the light it receives.

To achieve realistic lighting, ray tracing recursively traces secondary rays. When a primary ray hits a surface, new rays are generated to simulate reflection, refraction, and shadows. A reflection ray bounces off the surface according to the law of reflection, simulating how light would bounce off a mirror. A refraction ray passes through transparent or translucent surfaces, bending according to Snell's law, simulating phenomena like light passing through glass or water. Shadow rays are cast from the intersection point towards light sources to determine if the surface is in shadow.

This iterative process of tracing rays and their interactions allows for highly realistic rendering, accurately depicting complex lighting effects like soft shadows, specular highlights, and global illumination. However, the computational cost of tracing millions or billions of rays can be significant, making it a more resource-intensive technique compared to other rendering methods.