Forum

Author Topic: Manually placed Markers not working  (Read 4648 times)

engelbeck

  • Newbie
  • *
  • Posts: 35
    • View Profile
Manually placed Markers not working
« on: September 15, 2017, 07:02:45 AM »
I am frustrated by the lack of effectiveness of manually placed markers to help in image alignment!  I have over 300 photos of a car that I have masked out the background and placed almost 70 manually placed markers at well defined locations.  Frequently there are 5 or more markers on each image.  I tried setting the max number of key points to 1, 5, 10, and 20.  Alignment was awful.  I broke the images into 5 chunks ensuring common markers across chunks and could not align the chunks. 

I have to be doing something wrong!  Where is a good tutorial about aligning images manually

engelbeck

  • Newbie
  • *
  • Posts: 35
    • View Profile
Re: Manually placed Markers not working
« Reply #1 on: September 16, 2017, 08:57:03 PM »
 :-\  humm..no replies.  Has anyone successfully used markers to assist alignment?  What were the max key point and tie point settings.  What quaily setting did you use?  Hi or low? What else did you have to do to successfully align the images?

SAV

  • Hero Member
  • *****
  • Posts: 710
    • View Profile
Re: Manually placed Markers not working
« Reply #2 on: September 18, 2017, 09:09:37 AM »
Hi engelbeck,

You should NOT reduce the max number of key points to match the number of manual markers. If you reduce this number to your chosen values, it will be impossible for PhotoScan to match and align the images because it has only 1, 5, 10 or 20 points to compare in each image (which is insufficient).
Note that key points are the points that PhotoScan's Structure-from-Motion (SfM) algorithm is automatically extracting from all the images. The best quality key points (= tie points) will subsequently be used to form the sparse point cloud.

You need to keep the key point limit at 40,000 and the tie point limit at 4,000 (default values).

The manually placed markers are an additional source of information that PhotoScan will use. Keep in mind that even if you use manual markers, you need an adequate amount of image overlap to get a good 3D reconstruction.

Also make sure to have CONSTRAIN FEATURE BY MASK ticked in WORKFLOW > ALIGN PHOTOS. If uncheckd, your masked background will be used as well (which could be an additional reason for poor alignment results).

I hope that helps.

Regards,
SAV

P.S. If you still have problems, then please share some screenshots and/or your processing report. 

« Last Edit: September 18, 2017, 09:11:15 AM by SAV »

engelbeck

  • Newbie
  • *
  • Posts: 35
    • View Profile
Re: Manually placed Markers not working
« Reply #3 on: September 19, 2017, 11:18:39 AM »
Thanks SAV!  You have given me valuable direction.  I was trying to get the markers to dominate or be weighted more than the key points.  I will adhere directly to your recommendations and see where this goes.

SAV

  • Hero Member
  • *****
  • Posts: 710
    • View Profile
Re: Manually placed Markers not working
« Reply #4 on: September 19, 2017, 11:51:56 AM »
No worries, engelbeck.

Please keep me/us updated about the outcome/progress.

Regards,
SAV

engelbeck

  • Newbie
  • *
  • Posts: 35
    • View Profile
Re: Manually placed Markers not working
« Reply #5 on: September 23, 2017, 04:16:06 PM »
Same outcome when I set Key points to 40,000 and Tie points to 4000.  I looked at the Alignment processing report and there is not much of value there except the setting I used for the last Chunk processed.  All the graphics are pretty messed up.  What screen shots are you looking for?  Model? Single Image?

SAV

  • Hero Member
  • *****
  • Posts: 710
    • View Profile
Re: Manually placed Markers not working
« Reply #6 on: September 25, 2017, 12:28:15 PM »
Please share your processing report and a screenshot of your sparse point cloud including camera stations/photos and markers.

You could also share all your pictures so the community can try to assess the issue.

Regards,
SAV

engelbeck

  • Newbie
  • *
  • Posts: 35
    • View Profile
Re: Manually placed Markers not working
« Reply #7 on: October 06, 2017, 06:43:19 AM »
Hi SAV,
    I promised I would report back.....setting Key points to 40,000 and Tie points to 4000 made o material difference.  I even divided the project into chunks based on my experience with which groups of images would align.  Couldn't get chunks to align.  I am going back to basics to improve w the quality of images in hope that I will succeed and that will be the cause of my problem.

SAV

  • Hero Member
  • *****
  • Posts: 710
    • View Profile
Re: Manually placed Markers not working
« Reply #8 on: October 06, 2017, 11:56:41 AM »
Hi engelback,

Maybe it is the object itself that causes problems. You mentioned that you try to reconstruct a car. The overall shiny/metallic surface as well as reflections on glass surfaces might be quite an issue for photo alignment.

Regards,
SAV