It supposed to have it natively :
Disrupt: Powering Watch Dogs
Assassin’s Creed's time-hopping gameplay demands the use of the Anvil and AnvilNext engines, while Far Cry’s expansive worlds require the services of Dunia. For Watch Dogs, Ubisoft Montreal’s design documents contained ambitious plans that failed to align with the strengths of Ubisoft’s internal engines, or those of third parties. As a result, Disrupt was developed, enabling seamless multiplayer, complex AI systems, and modern-day urban worlds filled with detail.
As a product of the new generation of games, Disrupt features all of the technologies enthusiasts desire, such as deferred lighting, dynamic weather, real-time dynamic reflections, pre-baked Global Illumination, subsurface scattering, and multithreaded rendering across all CPU cores. SLI, 3D Vision, 4K, and 4K Surround support is included, too.
http://www.geforce.com/whats-new/guides/watch-dogs-graphics-performance-and-tweaking-guideHopefully a fix is incoming from the devs.