create a search structure from a matrix of coordinates and one of directional vectors to be processed by vcgRaySearch
setRays(coords, dirs)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
an object of class "mesh3d" (without faces) and the vertices representing the starting points of the rays and the normals storing the directions.