How to stitch a Linear Panorama with source images taken from different positions?

[Gary Mansell]

Dear all,

I have done several normal (pictures taken from on point) Rectilinear
and Cylindrical Panoramas using Hugin, Autopano and Enblend and have
been very happy with the results.

I thought that I may like to progress and try my hand at what I think
is called a Linear Panorama. It is my understanding that this is done
by taking a series of photos of a view from incrementally different
camera positions.

It seems to my that this would be the ideal method of creating a
Panorama of a row of Beach Huts, so to this end, I have taken a series
of 15 photos of beach huts - all from the same distance from the huts
but incrementally moving along in the horizontal plane with my camera
so that each image was taken directly in front of each beach hut in
sequence. I ensured that each picture had a 50% overlap to ensure that
there was enough image to work with.

I have tried to follow the tutorial outlined on the Hugin Tutorials
Page - http://www.dojoe.net/tutorials/linear-pano/ but I have had no
sucess. The result is just a messy jumble of images.

Please can someone advise me how I can carry out a Linear Pano
sucessfully.

Any help gladly received.

Best Regards

Gary Mansell

[Bruno Postle]

On Wed 22-Nov-2006 at 08:43 -0800, Gary Mansell wrote:
>
> It seems to my that this would be the ideal method of creating a
> Panorama of a row of Beach Huts, so to this end, I have taken a series
> of 15 photos of beach huts

> I have tried to follow the tutorial outlined on the Hugin Tutorials

> Page - http://www.dojoe.net/tutorials/linear-pano/ but I have had no
> sucess. The result is just a messy jumble of images.

The only general bits of advice I can offer are:

* Correct lens barrel distortion in your images before you start,
you can't do this in the stitching process as you would normally.

* Only pick control points in the same 'plane', ie. only use the
front walls of the beach huts.

* Experiment with just two pictures.

--
Bruno

[Gary Mansell]

Hi,

Thanks for your advice - I think that it is a good idea to start with
just three images to start with as you suggest.

Presumably, I would want to anchor the central image for position - and
according to the tutorial mentioned above, this picture should have
it's own lens with the x and y shift (d & e) parameters set to be
inherited. The other pictures should all use a different lens with the
x & y shift (d & e) parameters set to be not inherited.

Presumably, I should then do an optimisation run just to determine
barrel distortion for all pictures?

Then, I guess that I need to do a lens shift optimisation to position
the pictures correctly?

Then, do the anchor roll optimisation on the anchor image only.

The finally x shift (for finetuning), roll (rotation) and fov (zoom)
(parameters d, r and v); again, second lens not checked, as well as
your anchor image in the "roll" list

What do you think?

Best Regards

Gary

[Bruno Postle]

On Thu 23-Nov-2006 at 03:29 -0800, Gary Mansell wrote:
>
>Thanks for your advice - I think that it is a good idea to start with
>just three images to start with as you suggest.
>
>Presumably, I would want to anchor the central image for position - and
>according to the tutorial mentioned above, this picture should have
>it's own lens with the x and y shift (d & e) parameters set to be
>inherited. The other pictures should all use a different lens with the
>x & y shift (d & e) parameters set to be not inherited.
>
>Presumably, I should then do an optimisation run just to determine
>barrel distortion for all pictures?

My workflow would be something like (note this is for stitching
photos taken from _different_ locations):

1. Correct barrel distortion, ie. you need a set of images that
don't have any lens distortion before you start stitching.

I'd do this by stitching a 'normal' panorama and recording the a, b
& c parameters (though there are various other methods). To correct
the images, you can do it: in the gimp plugin, hugin one at a time
or on the command-line with fulla.

If you have a very expensive lens or the images are telephoto then
you don't have barrel distortion and you can skip this step.

2. Load the anchor image into hugin, use horizontal and vertical
control points and optimise roll, pitch & yaw to straighten it.
Then fix this position, you can even delete the control points.

3. Load the other images, set lots of control points in the 'plane'
that you want to align.

4. Uncheck inherit for d & e shift parameters and optimise them for
all the additional images to get an approximate alignment.

5. Uncheck inherit for roll, pitch, yaw & fov as well and optimise
again to get a better stitch.

--
Bruno

[Gary Mansell]

Thanks for your advice Bruno - I will give it a go using your workflow.