Quad Software, makers of Grome, have just released the Graphite Renderer.
Graphite is a high-performance outdoor rendering middleware suitable for rendering large terrain surfaces, water and vegetation layers. The library is designed to be quickly integrated into any engine or application using DirectX9 or DirectX10 rendering API for Window PC platform. The renderer is 100% compatible with Grome modeler application but can be modified to accept input from various data sources.
Of course, it’s meant to be used with Grome but they ship API’s and tools to use it with a variety of tools.