Photo realistic 3D rendering is not just for fun and hobby.
It is big business.
Many industries employ photo realistic renderings.
These include fields such as film and movie making, interior design, graphic design and product design.
What is Ray tracing? It is a technique of generating an image by tracing the path of light through pixels in an image plane.
The technique can produce images of higher realism that scanline rendering methods In the past, Ray tracing was considered very high end and advanced.
However, it is no longer the case.
Rendering and virtualization technologies have approached the state of hyper realism.
In hyper realism, renderings and physical reality are very hard to tell apart.
This is because many of the rendering systems and algorithms have become physically accurate in terms of simulation and calculation.
The latest technology for photo realistic rendering that had gone beyond basic ray tracing is Global Illumination.
What is Global Illumination? It is a collective term for several technologies (including raytracing and radiosity) that are used to produce realistic renderings via direct as well as indirect illumination calculations.
Global Illumination consists of algorithms that take into account not only the light which comes directly from light sources, but also where light rays from these sources are indirectly reflected onto other surfaces in the 3D environment.
Of the the most realistic technology for Global Illumination rendering is the usage of HDRI environment maps.
HDRI stands for High Dynamic Range Imaging.
This technology allows a greater dynamic range of exposures than normal digital rendering techniques, thus producing true-to-life imageries.
These are just some of the rendering technologies available.
It is certainly not an exhaustive list.