The research on Photo-Realistic rendering intends to develop algorithms in order to render images of synthetic or artificial high quality models. One of the most popular methods that allows to obtain this kind of images is ray tracing. This technique requires the evaluation of a very large number of light contributions in a scene that could be defined by several hundred thousand objects. To this end, the ray tracing algorithm must calculate a large number of ray-object intersections, which makes this algorithm very expensive in computation time. Fortunately, ray tracing is an algorithm intrinsically parallel which offers several potential acceleration techniques to reduce such higher rendering time in generating one single image.
This paper presents a survey of the parallel processing for the image synthesis by means of ray tracing. Firstly, we describe the ray tracing algorithm and the different sequential acceleration techniques briefly. This paper focuses on the different parallelization strategies of ray tracing. These strategies are presented from the point of view of their main differences, as well as their advantages and disadvantages. Afterward, we analyze the main interesting and promising research fields on the ray tracing acceleration technique, although these same fields can also help in other rendering algorithms.