@box said:

You drew the green rectangle outside the context of the terrain.
Open the terrain group for editing then draw your rectangle on it.

Ok, how many clicks do i have to do on the terrain? 1 or 2 because both looks like an edit mode.

Hello,

via the sandbox tool i created a new terrain. At the moment it's flat, no terrain modifying
was done yet. Now i drew vie line tool a rectangle on the terrain and painted it with a certain material.

So far ok:

Now i'd like to model the terrain. However when i change the terrain, the shape now partially disappear below the terrain.

So my question:
How can i draw shapes onto a terrain? How can i change the materials of this shapes at any time? How can i change the terrain after drawing a shape while leaving the shape as it currently is?

thx