How to find the rotation of the entity?

Developers Ruby API
6

I’m sure this later one is much improved, but FYI, it’s almost ten years since I did this code below, as part of a bigger example over on SketchUcation.com…
I added modules etc to tidy it up here…
You pass a transformation tr with 0.1.2 or x,y,z axes…
The # sections in the rot’ methods are older alternatives that will sometimes not give the same results…
Usage example:
rotx = TIG::Transformation.rotX(transformation)

module TIG
module Transformation
 def self.euler_angle(tr, xyz=[])
  m = tr.xaxis.to_a + tr.yaxis.to_a + tr.zaxis.to_a
  if m[6] != 1 && m[6] != -1
    ry = -Math.asin(m[6])
    rx = Math.atan2(m[7]/Math.cos(ry), m[8]/Math.cos(ry))
    rz = Math.atan2(m[3]/Math.cos(ry), m[0]/Math.cos(ry))
  else
    rz = 0
    phi = Math.atan2(m[1], m[2])
    if m[6] == -1
      ry = Math::PI/2
      rx = rz + phi
    else
      ry = -Math::PI/2
      rx = -rz + phi
    end
  end   
  return -rx if xyz==0
  return -ry if xyz==1
  return -rz if xyz==2
  return [-rx,-ry,-rz] if xyz==[]
 end
 ###
 def self.rotX(tr)
  #(Math.atan2(self.to_a[9],self.to_a[10]))
  #Math.acos(self.to_a[5])
  self.euler_angle(tr, 0)
 end
 def self.rotY(tr)
  #(Math.arcsin(self.to_a[8]))
  #Math.acos(self.to_a[0])
  self.euler_angle(tr, 1)
 end
 def self.rotZ(tr)
  #(-Math.atan2(self.to_a[4],self.to_a[0]))
  #Math.asin(self.to_a[4])
  self.euler_angle(tr, 2)
 end
 def self.rotXYZ(tr)
  self.euler_angle(tr)
 end
end
end
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