Time for some terrain questions again

I get some shadows in my terrain and that would be just great.
But they have no origin. Don't know where they come from.
I just have a terrain and nothing more. They are generated
with the Environment Sun turned on. With Sun turned off
they are gone.

My Sun setting (using the sun image from the EE3 installation)


Terrain with Sun on


Terrain with Sun off



Any idea on this?

behind the mountain is there terrain to cover up the other side? from what I know if there is no triangles on the other side the sun light will just go on, the splatters would be the triangles that can be seen from that angle(the suns direction). I would believe either adding terrain to cover it from the sun direction might work, or simply disable material culling on the terrain materials.

Judging from the mountains very varied slopes that is what is occuring.

Aaah... I'm at work now, but will certainly have a check this evening.
Thanks for the suggestion.

I can confirm Zervox's explanation of the problem is what is happening, as I had the same issues. I simply ensured all the outer pixels of my heightmap were at zero height and that worked.

I also had to add a simple square plane under my terrain as I had issues with light/shadows being cast on objects whilst the sun was underneath the terrain too!

Thanks guys.
I'm importing terrains (height, alpha and texture maps) from L3DT.
Guess the simplest way to solve this is then to add a thin black border
at the height map texture border before importing.