A graphics middle-ware engine developed by 4A Games for use in their video game Metro 2033, published by THQ. It supports Direct3D APIs 9, 10, and 11, along with NVidia's PhysX, and also NVidia's 3D Vision.
The engine surprised everyone when first came out, and now on metro Last Ligh Redux, we can see the quality and power of the engine, which is absolutely beautiful.