It is a common misconception to think that ray-tracing gives physically realistic results. Since only one ray is sent out per pixel, it gives us reflections, refractions, and hard shadows, but it doesn't give soft shadows, caustics, and global illumination (which are all required to achieve photo realism). To get a truly realistic rendering, we can use path tracing. Instead of sending out one ray it sends out tens, hundreds or even thousands of rays for each pixel to be rendered. When it hits a surface it doesn’t trace a path to every light source, instead it bounces the ray off the surface and keeps bouncing it until it hits a light source or exhausts some bounce limit. It then calculates the amount of light transferred all the way to the pixel, including any color information gathered from surfaces along the way. It then averages out the values calculated from all the paths that were traced into the scene to get the final pixel color value. This is insanely expensive, but there are many optimizations available and many believe this is the future of high quality rendering. (Credit: 148 lecture and https://www.dusterwald.com/2016/07/path-tracing-vs-ray-tracing/)
It is a common misconception to think that ray-tracing gives physically realistic results. Since only one ray is sent out per pixel, it gives us reflections, refractions, and hard shadows, but it doesn't give soft shadows, caustics, and global illumination (which are all required to achieve photo realism). To get a truly realistic rendering, we can use path tracing. Instead of sending out one ray it sends out tens, hundreds or even thousands of rays for each pixel to be rendered. When it hits a surface it doesn’t trace a path to every light source, instead it bounces the ray off the surface and keeps bouncing it until it hits a light source or exhausts some bounce limit. It then calculates the amount of light transferred all the way to the pixel, including any color information gathered from surfaces along the way. It then averages out the values calculated from all the paths that were traced into the scene to get the final pixel color value. This is insanely expensive, but there are many optimizations available and many believe this is the future of high quality rendering. (Credit: 148 lecture and https://www.dusterwald.com/2016/07/path-tracing-vs-ray-tracing/)