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Alignment Error - Tries again after additional scans.

There are times, particularly when transitioning between rooms, stairs, or down hallways, where I get an alignment error for one reason or another. I then have to move the camera back, make a new scan, and then re-scan the original position a second time. It would be really nice to see Matterport make a second (or more) attempt to realign a scan after moving the camera back for a new scan so I am not having to scan the same areas twice, thereby saving me time.

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17 comments
  • Oh, great call, @smithcolin, and something we've been considering here! If you don't mind me asking, how often does this situation arise? 50% of your models, 10%, more, less?

  • Hey @MP-Scott,

    I am a new user and so far I have had it happen 100% of the time of 4 models I've created. :) I've been trying to be a little more careful about spacing things out not too far but it still seems happen and is a big time drag. Especaially if I've already moved the camera and started the next scan when it gives me the error message, thereby deleting 1.5 scans at that point in time.

  • Woah! 100% is a lot! Just to double-check, you're generally moving 5-10 feet per scan, but maintaining a line-of-sight to at least one prior scan, correct?

  • Trying to stay 5-10 feet apart with line-of-sight. I find it happens most while moving between rooms, particularly small bathrooms. I do always do a scan on each side of the door as well. I'm sure it's still user error and part of my learning curve at the moment.

    And by 100% I meant that it's happened on average 2-5 times for each of the 4 models I've created... not 100% of the scans I've done.

  • Good to know! If you're up for it, feel free to post a model or two to the Support from the Community section, and perhaps ask for any tips or feedback on scanning. I'm continually learning from the folks here! I'll take a look also!

  • After scanning a while, you may start to predict when you think the camera might run into a problem.

    When I am unsure, I'll often scan in two directions at once so that I can keep moving and if it doesn't pan out in one direction, the next shot has a chance of completing. This is often something I do in hallways or areas with multiple mirrors. Scan a tricky one, scan a safe one, repeat.

  • Hi @smithcolin When one first starts out it's pretty common to have non-alignments due to moving the camera too far based upon the previous scan point. The 'next' scan point has to have enough data from the 'previous' scan point for the 'next' one to know where it is at, as the 3D model builds.

    I recommend scanning more closely in the beginning than may actually be necessary until the confidence is there to move further apart. More scans only helps build with more data, and unwanted scans can be turned off in Workshop. When transitioning between rooms a scan point directly in the middle of the door may be necessary, especially with small bathrooms. I'll often offset the camera into the room a bit with two tripod legs in, and one out.

    When scanning a room with a mirror, try to scan all points in the room before scanning close to the mirror. The 'large data' of the room can help the 'mirror' scan align better.

    When going down hallways, you may need to move only 2-3 feet depending on how long it is before a doorway or object to create a 'break' in one of the walls.

    If you get a low overlap, do not delete the scan. Instead, just go back and scan between the 'prior' and 'low overlap' scans to fill in the data.

    For me, I'd rather not have MP 'store' the non-aligned scan point as it would be difficult (at least for me) to know exactly where to place the camera on the subsequent scan point.

  • There is definitenly a learning curve when it comes to using this camera, but overall it's been a good experience.

  • Great notes, @Bill!

  • I hadn't thought of that -- clever strategy, @Chris Hickman!

  • MP should not market the camera as "easy to use", as the hardware are easy to use but it does take some trail and error as well as experience gained to become efficient in completing Spaces. Had a lot of re-scans when I started out but its now way less. :-)

  • Fair point, @JC Coetzee! Question, if you don't mind: What 1-2 things really accelerated your scanning? In other words, once you learned those, you saw your failed alignments decrease, and your speed/comfort with the system increase?

    ...Obviously, the more we can ease these parts, the better!

  • My first scan looked like a pin cushion. I scanned so close together, and it took forever to complete. Since I have learned where I can go, and how far I can push the camera as far as distance between scans, now it goes a lot quicker I have no problems deleting a couple of scans that don't align, and working forward again.

    I would say scan your home for a day. Start outside the front door, work your way in, then just keep scanning. Don't upload the models. Just scan.

    Pay attention to the following:

    • Exterior scans to interior scans
    • Moving through doorways, always scan outside center of the doorways if they lead into a hallway.
    • The sun shining in on the floor or wall (you will not be able to scan those spots but they will show up in the model, it is best to close the shades some if possible)
    • Note how you can scan outside if the sun is not shining on the area
    • Test how far you can walk the camera before it tells you it could not align the scan.
    • Think of how the user is going to move through the home: put scan points where you think they will be walking, especially at corners, like a hallway that has a 90 degree turn.

    I'd say that 3 models of your home and you got it. (pretty much)

  • Hi @jrbatchelor. Great comments and tips for those starting out. The only thing I'll add is I strongly recommend always starting the Space with the interior. One is more prone for alignment issues if doing any exterior first. As much as possible I save exterior until the very end, or at least until I have the interior walls scanned that abut the desired exterior scan points

  • @MP-Scott, I have read a lot on the "we Get Around" forum and Dan also gave very good advice and tips (imho he is THE greatest supporter and promoter of Matterport) and I also got tips here on this forum. Then I also did a lot of test scans and played around with the camera. Only way to learn and get a feel for the camera is to use it. On each project I learn something new, and adapt my scan technique accordingly.

  • @jrbatchelor, I would agree with @Bill. First start inside and move outside last.

    I usually do about 10 scans and do an upload and then continue with the Space. This way I can get a small sample of the Space before leaving and have an idea of how the rest of the Space will look.

  • Bill, I totally agree that the Capture App should highlight or put an extra circle around the scan position (in red?) to show exactly which scan position it has just computed (Aligned).

    One thing that we noticed that may be contributing to "incorrect alignments" not being detected by the user is that the Capture App screen turns black and zooms out to show the whole model.

    In my opinion, it shouldn't do that - you lose the spot where you staring at (if you were staring at it).

    If anything the App should slowly traverse (pan) from the current view and center on the scan that just aligned and draw a red dotted circle around just that position.

    The numbering of the scans are obviously the way to determine which is the highest number but it can be a bit hard to find in a large model.

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