1. A method of displaying caustics, the method comprising: actuating a graphical processing unit (GPU) to determine intersection positions on a second object, at which rays emitted from a light source that have passed through particles of a first object meet the second object, by calculating intersection positions only for particles directly visible from the light source among the particles, apply caustic textures to the intersection positions at the second object, generate a caustic map by connecting the caustic textures to each other by caustic lines, and render the first object using the caustic map based on a result of the applying of the caustic textures to the intersection positions to generate a three-dimensional (3D) image comprising the rendered first object for display.