[ptx] Looking for expertise on optimizer internals

[Littlefields - Rik, Janis, Kyle & Peter]

I am working on internal improvements to the Panorama Tools optimizer, 
and I am looking for other people to talk with about this.

Briefly, I have working prototype code that changes the way that the 
lmdif optimizer is called.  The original code seeks to optimize distance 
squared, where distance is what lmdif sees.  My mods also seek to 
optimize distance squared, but the formulation is to optimize dx^2 + 
dy^2, where dx and dy are what lmdif sees.

The change in formulation gives lmdif better information about how to 
change the parameters, leading to faster and more accurate convergence.

But of course there are wrinkles dealing with wraparound and near-polar 
points, and I would like to tap into whatever other people know about 
the optimizer, to be sure that I don't mess things up..

If you have experience with the guts of adjust.c and are willing to 
share it, please chime in.

Thanks very much,

-- Rik Littlefield