Angles are only defined between two vectors, so finding the angle between a vector and a plane can vary depending on which vector in the plane you're interested in. Most of the time, the vector you're interested in is the angle between the vector and it's projection into the plane which can be calculated using the face.plane method and the Array.project_to_plane method. The only trick here is that vectors are not points, so you would have to either pick a point in the plane, then transform it by your vector or translating the plane to the origin and simply calling the vector3d.to_a method. As it turns out, the second method is much simpler since given a plane of of the form [x,y,z,c] then translating it to the origin is as easy as changing it to [x,y,z,0]. Here is the code
def angle_between_vector_and_projection(vector,face)
plane = face.plane
plane[3] = 0
projection = Geom;;Vector3d.new(vector.to_a.project_to_plane(plane))
return vector.angle_between(projection)
end
