CPfind creates few or no control points

[Adam Kimber]

Hi. I have been attempting to get Hugin to stitch photos from my camera phone for a couple of years with little or no results. I kept thinking it was some bug and it would be fixed in the next version. However maybe I am doing something wrong. I am not sure what though. I also get errors on some of the options on control point finders.

I am running 2016.2.0 on Windows 10 x64.

Many thanks for your time

Adam

[Roger Broadie]

Adam,

Well, well: one lives and learns. I have stitched a number of perfectly satisfactory panoramas using photos from my rather basic mobile phone, though, I admit,
with the aid of Ptgui rather than Hugin. I therefore assumed that Hugin would work similarly. In fact I hit just the problem you did, with Cpfind failing to discover
any control points, or, in one case, a tight cluster that did not permit a satisfactory stitch.

A little playing suggested that the problem was that Cpfind (and probably, I guess, other cp detectors) needed at least a rough idea of the field of view to discover
a useful set of control points. In the case of my phone (a Moto G3) there was Exif information that the focal length was 3.64 mm, but nothing to allow that to be
turned into a field of view. On some basis or other, Hugin assigned a fov of 156 degrees, which is absurdly large. When I substituted 65 degrees, which is the
approximate fov for a full set of lens parameters a-e, Cpfind produced a set of control points that allowed the stitch to proceed.

In your case there is, as far as I can see, no Exif information in the images you attached and one is presented with a screen to enter lens information. I put in 60
degrees and got 25 control points. With a little work to refine the control points and lens parameters I got the attached stitch (reduced-size version) and pto file.
The optimised lens parameters suggest that 65 degrees might be a better starting value for the field of view.

I too am using Hugin 2016.2 on 64-bit Windows 10.

Roger Broadie



========================================
Message Received: Feb 01 2017, 10:19 AM
From: "Adam Kimber"
To: "hugin and other free panoramic software"
Cc:
Subject: [hugin-ptx] CPfind creates few or no control points

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[Stefan Peter]

Dear Adam Kimber

First, please refrain from sending images as attachments to mailing
lists. There are plenty of services allowing you to upload images for
free and then just post the link to them.

Secondly, one of the screenshots you posted has the clue for solving
your problems. The error message "Could not find autopano-sift-c.exe in
path" leads me to the assumption that you had installed an earlier
version of Hugin on your PC and when upgrading, did not reset the
preferences.
Autopano-sift-c as a control point detector has been abandoned some time
ago because the licensing for commercial usage was not allowed. However,
if you have installed a version prior to this and not updated your
preferences when upgrading, Hugin still will try to use an application
(autopano-sift-c.exe) for determining control points which is no longer
distributed with Hugin.

So, in order to fix you issues, please go to File -> Preferences and
then to the "Control point detectors" tab. There, you have to press the
button "Load Defaults" which will replace your outdated settings with
the ones that work.

Sorry for not being able to be more precise here, but I do not have
access to a Windows system at the moment.


With kind regards

Stefan Peter


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[Gnome Nomad]

My not-so-smart phone also fails to provide focal length reliably. Things seem to work well if I give it 60 to start with.

[Greg 'groggy' Lehey]

On Wednesday, 1 February 2017 at 2:17:03 -0800, Adam Kimber wrote:
>
> Hi. I have been attempting to get Hugin to stitch photos from my
> camera phone for a couple of years with little or no results. I kept
> thinking it was some bug and it would be fixed in the next
> version. However maybe I am doing something wrong. I am not sure
> what though. I also get errors on some of the options on control
> point finders.

I've read what the others have written, but there still seems to be
something missing. As they say, there are no EXIF data, so Hugin asks
for a focal length. But you don't mention that.

Most mobile phones have a relatively wide angle lens. I specified 30
mm, crop factor 1 for these images, and they aligned perfectly.

> I am running 2016.2.0 on Windows 10 x64.

There has been some question about this. But as Stefan says, maybe
it's your configuration with a hangover from older versions.

Greg
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[Roger Broadie]

I think it's worth adding a few points to follow up my previous post.

The problem with my own Moto G3 mobile phone seems to be that its camera produces an Exif file that contains enough to suppress the 'Camera and Lens data'
window that is shown on first loading images with no Exif file, but not enough to allow the real field of view to be determined. Specifically, I suspect that it lacks
information on the focal-plane resolution that is needed to allow the sensor size in pixels to be converted into linear dimensions in say millimetres. Under those
circumstances Hugin apparently uses the focal length from the Exif file (3.64 mm in my case) and applies a default crop factor of 1. That does indeed yield the
field of view of 156 degrees I met and which is so unhelpfully large that it suppresses the finding of any control points at all.

I have some sympathy with the comment from Greg 'groggy' Lehey (Thu 02 Feb 2017 at 07:26:04) that 'there still seems to be something missing'. The main
thing missing is an Exif file for the original photos. Perhaps there was one, but Adam stripped it out, possibly because it contained confidential information about,
say, location. If it had contained only partial information, he might well have found Hugin's CPfind utility failed to find any control points. After all, that is what
happened to me and is why, in the absence of anything more definite to the contrary, I am prepared to take Adam's subject-line 'CPfind creates few or no control
points' literally.

One would then have to assume that he never loaded the Exif-free versions into Hugin, because, if he had, he would have met the 'Camera and Lens data'
window. Just cancelling it without entering anything is enough to get the control-point finder off the ground, because Hugin - in the cases I tried - allotted the
images what I take to be its ultimate default, a field-of-view of 50 degrees. Or you could press Escape to close the window and simply create a few control points
by hand to give Hugin something to work on.

Roger Broadie


========================================
Message Received: Feb 01 2017, 07:35 PM
From: "Roger Broadie"
To: hugi...@googlegroups.com
Cc:
Subject: RE: [hugin-ptx] CPfind creates few or no control points

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