From Planetside Software:
Terragen 2 (64-Bit) is a solution for rendering and animating realistic natural environments. Create entire worlds from your imagination, or import real world terrain datasets and use Terragen 2 (64-Bit) to create the most realistic visualizations possible. You control the weather, landscape, rivers, lakes and oceans, suns, moons and stars. With Terragen 2 (64-Bit) you have complete control over the shadier networks used for terrains, textures, micro polygon displacements, clouds and objects distributions. You can reorganize the planetary shading pipeline to suit your goals. Place grass and trees wherever you want, as well as other objects in OBJ format that you can model in third party software. It's easy to find great plants and objects modeled by other Terragen 2 (64-Bit) users or elsewhere on the web.