Thanks guys.
Quotewould it be possible to populate imported objects such as your rocks with trees/grass?
Yes and no I'm afraid.
As far as I can tell, terragen populations will not read the surface as it would a planet surface.
I tried a few workarounds with no luck.
However, there are alternatives.
If you are creating a mesh from a flat plane, it is possible to use a displacement map generated from the sculpt as an offset for the population.
It's also possible to create distributions in other packages and import to terragen.
That's a workflow I often use for scene layout. (Example attached)
Chris