How to fade out patterns at all edges and vary the pull of patterns at the centre.

Hi,

I am trying to develop pattern using the attached code above the surface. AT present the pattern is varying according to a single point.  I need the pattern should completely fade out at all edges since it have to be attachable to my other parts.

Also I need to control the variation of pattern in its height and its closeness of packing at the centre portions.

Thank in advance.