This is the first time I see this feature. You know, when you capture a portrait photo with a low aperture f-number lens in a DSLR, the bright light areas appear like shiny bright sports in the background. The size depend son the diaphragm shape, the number of blades that the aperture has.
With mobile phones now mimicking this bokeh effect digitally, you usually get to see those bright area looking like circles. With the Galaxy S9 you can actually control the shape of those lights using bokeh filters and turned those background lights into different shapes, adding sparkle to the scene.
Without the effect, it will look like circles or you can change it to look like butterflies, music notes, rabbits, snowflakes,airplanes, flowers, twinkles, heptagons, hearts or stars.
I really like this idea and I think many people will enjoy playing with it to enhance their portraits. Oh, by the way, unique bokeh filters can be achieved with DSLR cameras as well using laser-cut custom bokeh filters that you put in front of the lens you are shooting with like a lens filter, so this idea actually comes from a well-known method used with standard cameras and Samsung brought it to the S9 in a digital form.