Hi

Is there a way to change the default square shape of the terrain object?

I don't mean the terrain height which can be controlled with functions or gradient images, I mean the actual object which is always a square platform. For a certain effect, I need it to be round.

Clip it simply from the bottom, then you do not have the square bottom.

One day your ship comes in - but you're at the airport.

You sculpt a round terrain (either by hand or by importing an image) and then clip off the bottom using the clip slider. See the attached image.

Ciao
TD

Ooops, too slow...

 Thanks, I know about the clipping technique.

Unfortunately I don't think this can work with my terrain - a procedural one driven by terrain fractals.

You see, my goal is not a round mountain. I want a round platform to be the basis for large scale desert canyons.

Ok, I figured it out eventually. I used a round black & white image as a texture map node in the function editor. I then used a subtract blending mode in a kombiner with the rest.
That gave me a round elevated terrain, retaining exactly the same terrain features I had before.

Finally I used clipping until the square floor got cut off completely. 

Thanks everyone for the inspiration!

If you're doing a pure procedural terrain, you're probably best doing the clipping via some nodes rather than an image.