nVidia's OpenGL nature scene code sample

NVIDIA has posted an OpenGL nature scene code sample. The demo combines several techinques to produce a realistic looking natural scene. The gently swaying grass is rendered using transparency anti-aliasing to ensure realism even in the distance; and the horizon is tinted using an exponential fall off effect. Several textures and a pixel shader are used to create the diverse terrain. A whitepaper is included that explains all of these techniques in detail.

(text taken from DevMaster.net)

The rendering is very impressive.