Global optimization
p1,2
p4,4
p3,4
p4,1
p3,3
p1,1
p1,3
p2,4
p2,2
I1
I2
I3
I4
Minimize a global energy function:
What are the variables?
The translation tj = (xj, yj) for each image
What is the objective function?
We have a set of matched features pi,j = (ui,j, vi,j)
For each point match (pi,j, pi,j+1):
   pi,j+1pi,j = tj+1tj