3-D interference patterns can exist in real life, as any two waves traveling in three dimensions will produce such patterns. While the classic Young's double slit experiment demonstrates 2D interference patterns on a screen, the underlying principles apply to 3D scenarios as well. Achieving a visible 3-D interference pattern can be complex and may require specific setups, such as using multiple slits or wave sources. The discussion emphasizes that 3D interference occurs naturally in various environments. Understanding these principles can lead to practical applications in fields like optics and wave physics.