What can this do
Generate 3D Terrain Procedurally
Export Terrain as OBJ
You can write and test your own shaders
An Inbuilt IDE for shaders
A Node based as well as Layer based workflow

Save the project(custom .terr3d files)

Height map visualizer in node editor

TerraForge3D is a Free And Opensource Procedural Terrain And Modelling Tool. This is a free alternative to paid softwares like Gaea or World Machine. This has got everything you need to make any sort of terrain you want to. This is very easy to learn and use!