anchor.diff:  \vec{P'}=P_0a\vec{X}+P_1b\vec{Y}+P_2c\vec{Z}+\vec{T}
   ++++
   
  -This is the same as extend stem:[\vec{P}] to a 4 component vector stem:[\vec{P}(P_0,P_1,P_2,1)] and multiply by matrix stem:[M]. Now what does inverse matrix stem:[M^{-1}] mean? In this case it represents a world to local transform, so if we multiply stem:[\vec{P'}] by stem:[M^{-1}], we should get stem:[\vec{P}] back. How do we transform the point stem:[\vec{P'}] in world space back in local space? We subtract the local space origin (aka the translation stem:[\vec{T}]), then dot each axes to get its local space coordinate and rescale it:
  +This is the same as extend stem:[\vec{P}] to a 4 component vector stem:[\vec{P}(P_0,P_1,P_2,1)] and multiply by matrix stem:[M]. Now what does inverse matrix stem:[M^{-1}] mean? In this case it represents a world to local transform, so if we multiply stem:[\vec{P'}] by stem:[M^{-1}], we should get stem:[\vec{P}] back. How do we transform the point stem:[\vec{P'}] from world space back in local space? We subtract the local space origin (aka the translation stem:[\vec{T}]), then dot each axes to get its local space coordinate and rescale it:
   
   [stem]
   ++++
  
positive.code: ++++
  
  Now it is clear what kind of calculation we need. We need 2x2 matrix multiply and multiply by adjugate: stem:[AB], stem:[A^{\#}B] and stem:[AB^{\#}]. We already know how to do adjugate, but in this case, adjugate can be combined with multiplication so we don’t waste instructions. Just expand the result and rearrange the order, for example:
  
  [source, c++]
  ----
  
negative.code: }
  ----
  
  Another trick is after we calculate the 2x2 sub matrix, for example stem:[\left|D\right|A-B(D^{\#}C)], the final adjugate to get stem:[X=(\left|D\right|A-B(D^{\#}C))^{\#}] can be combined with storing 2x2 sub matrices to the final result 4x4 matrix. You can see this at the end of the function.
  
  The only thing left if determinant. 2x2 determinant is easy, the problem really is the whole 4x4 matrix determinant. Remember the determinant property we give above:
  
  [stem]
  ++++
  