Compute the normal to each facet plane.
help cross
That will give you the normal vector. Add a multiple of the normal vector to the coordinates of each vertex.
Note that each vertex is shared by several facets. So you will need to compute the TOTAL, cumulative offset for each vertex, and only then move those vertices.
Oh, by the way, be careful. Depending on the shape, if your meshed surface is not a well-behaved convex surface, moving things around willy nilly can cause the surface to cross through itself.
