popoulus style

how could i go about making a real-time sphere editing system like the one in popoulus i.e. Raise land Lower Land.

I tried useing vertexcoords but it doesn't move them Relative.

convert their world coordinates to a relative coordinates by parenting a pivot at the vertices position.
point the pivot to the centre of the sphere and move it backwards/forwards to lower/heighten

then recreate the mesh


OR-------

Use VertexNX (search for the similar commands) and use those values to manipulate vertices in and outward.


I gota run- someone explain this one a bit more? :D

This demo lets you click on sphere vertices to 'pull them out':
http://www.blitzbasic.com/codearcs/codearcs.php?code=1008

Is that the kind of thing you mean?