According to NVIDIA’s senior vice president of content and technology, the first ray-traced games will be released as early as this year. Of course, these titles will only feature ray tracing sparingly, as it is computationally intensive: rendering will remain largely raster based.
Ray tracing has been the holy grail of graphics and was always a better-quality alternative to rasterization. Ray tracing simulates the physical properties of light, including reflection and refraction, scattering, and dispersion and propagation. It is computationally very intensive, and this was the main reason why it was dominating realistic, offline rendering.
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Source: [H]ardOCP – Ray-Traced Games Coming This Year