Ray-tracing how the light would bounce naturally

Ray-tracing is one of the most
important techniques solving the rendering equation (Kent and Williams, 1997;
Jensen, 1996). Since light in a scene affects the individual objects
indirectly, the Ray-tracing technique deals with complex light interactions. It
traces light through each pixel in the scene and creates realistic rendered
results of 3D scenes in 2D images. The ray directions are constructed through a
line between the virtual camera and the pixels, extending it into the scene
(Scratchapixel, 2017). The light ray passes through a number of bounces and
since the colour is a result of how much light return to the point of view, the
colour of each pixel is based on the light ray’s interaction with all objects
in its traced path. Because of it, Ray-tracing can simulate optical effects
such as reflection and refraction. The ray-tracing technique sends light rays
in the reflection and/or refraction directions trying to simulate how the light
would bounce naturally in each case considering the surface. For example,
considering a scene with a glass of water, ray-trace would simulate the
refraction of a light ray of a real glass of water by banding the light rays in
different directions to create the distorted effect of images seen through the
glass of water (Fig. 10). Resuming, Ray-trace involves the individual ray of
each pixel, the ray intersection with other scene objects and the object colour
in the intersection point (that can vary according to the object, how much
lights it receives and the object’s surface characteristics).