Is there any tutorial/snippet that would allow one to understand how to "convert" a png image into a terrain?
The searches I made only gave me the first step (http://wiki.blender.org/index.php/User:Hoehrer/Tutorial:_Creating_a_Heightmap_from_a_Plane) which creates the map itself…
I know that jME internal Terrain Engine works loading grayscale images to create a TerrainBlock. So, simply save your heightmap with the better image format for jME. Maybe JPEG, GIF or PNG should work properly but I heard of RAW too.
Furthermore pay attention that now Blender should be able to render Depth informations instead of Ray Tracing informations, simply using compositing nodes. Nodes are a really powerfull new feature of Blender.
I the past, I tried to load the TerrainMap from a OBJ file implementing an extension of the TerrainMesh class, but I was not so expert and my attempt was buggy.