r.x=(rand_get_double(&(md->random))-0.5)*md->dim.x*0.37;
r.y=(rand_get_double(&(md->random))-0.5)*md->dim.y*0.37;
r.z=(rand_get_double(&(md->random))-0.5)*md->dim.z*0.37;
r.x=(rand_get_double(&(md->random))-0.5)*md->dim.x*0.37;
r.y=(rand_get_double(&(md->random))-0.5)*md->dim.y*0.37;
r.z=(rand_get_double(&(md->random))-0.5)*md->dim.z*0.37;