Just found out it is no longer supported. Sad! 
Note: This is a legacy SDK. Developers may download and continue to use, but it is no longer supported. NVIDIA Ansel is a revolutionary way to capture in-game shots and share the moment. Compose your screenshots from any position, adjust them with post-process filters, capture HDR images in high-fidelity formats, and share them in 360 degrees using your mobile phone, PC, or VR headset. Sharing is even easier with GeForce Experience. Hit “Alt+Z” to open the in-game overlay and quickly share Ansel images to Facebook, Imgur, and Google Photos.