PanoTools mailing list archive

Mailinglist:PanoTools NG
Sender:pedro_silva58
Date/Time:17-Dec-2008 00:51:53 +0100
Subject:Re: Awful time stitching square suspended ceiling tiles :-(

Thread:


john, thank you for your reply.

--- In #removed#, "John Houghton" <j.houghton@...>
wrote:
>
> --- In #removed#, "pedro_silva58" 
> <pedro_silva58@> wrote:
> >
> > sorry for being so late to join the party, but i don't understand
> > the purpose of one cp per seam.  what parameters did you optimize,
> > and why?
> 
> I was merely making the point that by intelligent optimization and 
> making use of parameter values already known (applied by a template), 
> you can manage with far fewer control points than is the case if you 
> expect PTGui to evaluate everything automatically from scratch.  

your general point had been understood.

My 
> example was an extreme case, showing that only one point per seam 
> actually enabled a perfectly good stitch to be performed.  I already 
> knew the lens parameters (from calibration) and approximate yaw 
> values, and I knew that the pitch of all 4 images was the same and 
> the roll was also the same (since a spherical pano head was used).  
> So I optimised fov, yaw (of 3 images) together with linked pitch and 
> roll of all 4 images.  

again, i (think i) understand the general point.  what i don't really
understand is why -- since you knew the lens parameters (from
calibration) -- you felt you needed to optimize fov (and not, say, d
and e[*]).  i can't help wondering whether the custom fov from 4 cps
is really better than a previously carefully determined one.  i
suppose i could try myself, but i don't have a pano head i can trust
for that.  finally, i might have expected a champion of t1 points to
use them to optimize pitch and roll, rather than a single cp between
image pairs (maybe the appropriate features were missing?).  

> Of course I am not suggesting that you would 
> use only one point per seam in a general workflow.

yes, of course not!

please understand that i'm not (and was never) challenging you, or
anything of the sort.  i have the greatest respect for your skills, as
a photographer and panographer, as well as teacher.  i would not have
dared to optimize pretty much anything with so few cps, but was hoping
i'd learn yet something else from you.

[*] i think that whenever i suspend my camera from a long lens there
is enough play in the mounts that i can't trust the shifts to remain
unchanged.  i'd not be surprised if the same thing happened with a
fisheye, only less obvious. 

again, i appreciate your taking the time to reply. 

cheers,
pedro



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