Method: Geometry::Vector#angle

Defined in:
lib/geometry/vector/vector.rb

#angle(other) ⇒ Object

Return the angle (in radians) between self and the passed in vector.



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# File 'lib/geometry/vector/vector.rb', line 99

def angle(other)

  # Two options here:
  #
  # 1.  Math.atan2(other.cross_length(self), dot(other)) 
  #
  #     This is stable but slower (x 1.5)
  #
  # 2.  Math.acos(dot(other) / (r * other.r)) 
  #
  #     This is faster but unstable around 0 and pi where the gradient of acos approaches 
  #     infinity. An alternative way to view this is that the gradient of cos approaches
  #     zero and small differences in angle can be indistinguishable at some number of 
  #     decimal places.
  #
  
  # Math.acos(dot(other) / (r * other.r)) 
  Math.atan2(other.cross_length(self), dot(other)) 
end