Add Attractor:

Add Attractor:
 An attractor is defined with the following pattern:
 ATTRACTOR(xa;ya;za;a;b) where:
 xa;ya;za : coordinates of attractor point
 a        : desired size on attractor point
 b        : distance of influence of attractor

Formula computed is following: R-(R-a)*exp(-(r/b)^2)
with r : distance from attractor