# Ortho projection of 3D points with a vector

I have 3D points and I need to make an 2D orthographic projection of them onto a plane that is defined by the origin and a normal n. The meaning of this is basically looking at the points from the top (given the vertical vector). How can I do it?

What I'm thinking is:

1. project point P onto the 3D plane: P - P dot n * n
2. look at the 3D plane from the "back" in respect to the normal (not sure how to define this)
3. do an ortho projection using max-min coordinates of the points in the plane to define the clipping

I am working with iOS.