Orthogonal projection of a vector over a plane

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on orthoProjectVectorOnPlane vect, planeNormal
  -- calculates the projection (normal or orthogonal) of a free vector over a plane 
  -- both parameters are vectors
  -- vect is the vector we want to project
  -- planeNormal is a vector normal to the plane that defines its orientation
  -- only returns void (error) if planeNormal is (0,0,0)
  -- otherwise, returns a vector
  -- by Iñigo de Gracia
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  if planeNormal.magnitude <> 1 then 
    if planeNormal.magnitude = 0 then return void
    planeNormal.normalize()
  end if
 
  return planeNormal.cross(vect).cross (planeNormal)
end
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