[ptx] Optimization error report

[Jim Watters]

Hi everyone,

I have been working with Rik Littlefields, testing some bugs fixes for 
the optimizer.  We have discussed the possibility of modifying how the 
values for control point distance errors are generated.

Internally the optimizer calculates the distances differently based on 
the control point type.  Normal points are calculated as spherical 
distance.  Vertical and Horizontal points (T1 and T2) are only 
calculated using only one axis.  And Strait Lines T+ points are 
calculated as the distance the points are from the line.

But what is reported, is the actual distance the points are from each 
other after transformation, regardless of control point type.  This 
means that T1, T2, and T+ points will report their physical distance 
from each other. T0 points near the nadir and zenith may report Hugh 
errors when their spherical distance is very close together.  This 
report may be useful when creating rectilinear and cylindrical 
panoramas, but not for spherical.

We want the way the optimizer calculates errors to be the same as how it 
reports its errors.  This means that T1, T2, and T+ are reported the 
same way they are calculated.  No longer with huge meaningless values.

Currently dist is no longer used by the optimizer for T0 control 
points.  It is a possibility that for very large fov rectilinear and 
cylindrical panoramas calculating dist instead of distSphere would be 
more usefully.  Small errors in position of images far from the center 
will have larger error when displayed.  This is not proven yet.  It 
sounds good in my head.

What is the best thing to do for T0 (normal) control points?
1  - Use distSphere globally for optimizing and reporting for all formats.
2  - Use distSphere for optimizing and reporting for spherical and dist 
for rectangular and cylindrical.
3  - Have it overridable but default to 1
4  - Have it overridable but default to 2

It might be possible, but still unsure with no source to PTStitcher or 
the plugins and having several GUI's out there, whether an user option 
can be set to override any default.

I think the best thing to do is 2.  Then the user has the option of 
switching to distSphere for rectangular and cylindrical just by 
temporary setting the output format to spherical. 

Also internally the optimizer uses Root Mean Squared (RMS) of all the 
distances to check to see if it is any closer.  Currently an average* 
value is displayed in the message dialog and output script.  The changes 
will use RMS as an error indications for reported for the message dialog 
and the output script.  This will also eliminate the times when the 
message dialog would show the optimizer starting to climb instead of 
shrinking.  It is possible for rms to get smaller and have the average 
error increase.

* In the case of message dialog it actually displayed the sqrt of the 
average error, which is rather meaningless and misleading because the 
actual error is larger.

Before implementing these changes we are hoping to get as much feedback 
as possible.  We do not want to break anything.

-- 

 Jim Watters

 Graphic Software Developer
 http://members.rogers.com/jimwatters