element zeroLengthImpact3D $tag $slaveNode $masterNode $direction $initGap $frictionRatio $Kt $Kn $Kn2 $Delta_y $cohesion
As to $direction, 1 means out-normal vector of master plane points to +X direction. However I want to define the direction, whose out-normal vector of master plane points to negative X direction.
Can anyone tell me how to define it?
