create a search structure from a matrix of coordinates and one of directional vectors to be processed by vcgRaySearch
setRays(coords, dirs)
an object of class "mesh3d" (without faces) and the vertices representing the starting points of the rays and the normals storing the directions.
k x 3 matrix (or a vector of length 3) containing the starting points of the rays
k x 3 matrix (or a vector of length 3) containing the directons of the rays. The i-th row of dirs
corresponds to the coordinate stored in the i-th row of coords