Is it possible to add terrain system trees on a non-terrain object ?

Hi, Is it possible to add terrain system trees on a non-terrain object ? for example I want to add some trees in a room. Is there any way to do that?

No. You can't make use of the terrain system's method of drawing trees without actually using the terrain system (which including painting tools, tree swaying, billboard swapping at-a-distance, etc).

However you can place the tree prefabs themselves into your scene if you like, and they will act as standard models. You just won't get the optimised performance, painting tools, and features that you get from the terrain engine.

You could of course add a small completely flat terrain to you scene, where the ground level is just below the floor of your room. Then you could use the terrain engine itself to position and display your trees.