We developed a computational method to establish an interaction surface using virtual companion particles. Upon the implementation of this new method, wetting behaviors of liquid droplets on highly textured solid surfaces can be investigated by molecular dynamics (MD) simulations. The interactions between atoms in the liquid droplets and the "interaction surface" depend only on the distance from the atom to the surface. Textured surfaces with nanopillars can be modeled by setting the range of pillars. The interactions with the droplet atoms can be calculated by using the potential function of the virtual particles which are placed interactively on the range of pillars and the bottom surfaces. The positions of the virtual particles are determined so as to minimize the distance from the droplet atoms and can be set independently of the lattice structures of the solid surfaces. Hence, we can design various pillar shapes (e.g., cylindrical, cone, and pyramidal shapes) for the textured surfaces. Such a method can be useful for the MD simulation of wetting behavior on a complex rough surface with a simple and yet effective procedure.