Indirect lighting isn't a subtle effect, it's the difference between something looking real and looking fake. A lot of games go to great lengths to make the li

Indirect lighting isn't a subtle effect, it's the difference between something looking real and looking fake. A lot of games go to great lengths to make the lighting look sort-of-natural, but this takes a lot of manual effort by artists and it's usually mostly static. Real-time global illumination gets you realistic lighting without extra manual effort, and it enables dynamic lighting effects such as light pouring into a dimly lit room when a door is opened or the sun changing position in the sky over time. Ray tracing also has secondary uses, like determining visibility between arbitrary points in the scene or doing collision detection.