Explain the concept of ray casting in computer graphics.

Ray casting is a rendering technique used in computer graphics to generate realistic images by simulating the behavior of light. It involves tracing rays from the viewer's eye through each pixel on the screen and determining the color and intensity of the objects that the rays intersect with in the scene.

In ray casting, a primary ray is cast from the viewer's eye through each pixel on the screen. This primary ray is then tested for intersection with objects in the scene. If an intersection occurs, a secondary ray is cast from the intersection point towards the light sources to determine the amount of light reaching that point. The color and intensity of the object at that intersection point is calculated based on the lighting model and surface properties.

Ray casting can also handle effects like shadows, reflections, and refractions by recursively casting additional rays from the intersection points. For example, to calculate shadows, a shadow ray is cast from the intersection point towards each light source to check if any objects obstruct the light path.

Overall, ray casting is a fundamental technique in computer graphics that allows for the creation of realistic images by simulating the behavior of light and its interaction with objects in a scene.