Realign Scans (Beta)

This beta feature in the Matterport Capture application allows you to attempt to fix a misaligned scan by moving it to the correct place and re-trying the alignment process.

Previously, if you noticed that a scan succeeded but appeared to be in the wrong place on the 2D minimap view, your only recourse was to delete it, scan again and hope for a better outcome. 

With this feature you can:

    • Select the problematic scan location and move it to a more accurate location
    • Use two fingers to rotate the preview of the scan data to fix rotation problems. You can use the rotation preview like matching a puzzle piece - sometimes you can line up features between the main minimap and the preview of the individual scan to help confirm the right location (see below).
    • Corrections to one scan location automatically propagate through the rest of the model. For example, say you have completed a sequence of 10 scans, and notice that scan #4 misaligned to #3, but everything before and after #4 looks correct. You can select scan #4 and use Realign Scans; if that succeeds in fixing the location & orientation, all scans connected downstream of #4 will also shift. Since no adjustments to #5-10 are needed, you’ve fixed the scan job and can proceed. Example 2 below shows this with a real model.
    • Help improve alignment algorithms: corrections to misalignments help build future accuracy improvements.

This Beta feature is currently only available on the Android version of the Matterport Capture application. It will be available on the iOS version in the future. Please see matterport.com/beta for information about joining beta programs.

Example #1:

In this example below, scan locations #1 through #7 are correctly placed, but for some reason scan #8 has landed across the parking lot.  The algorithm thinks it is correct, so after capturing the scan, alignment was “successful”. However, #8 should be in line right above #7.

RealignScansexample1.png

To start, open the preview menu for scan #8 and select “Realign Scan”. 

realignscan.png

After preparing the scan data preview, you select the scan icon and drag it to the correct location. Use two fingers to rotate the preview, comparing the minimap preview to the piece of the map that moves with the scan. 

As shown below, sometimes this will provide a strong hint as to the correct location - we can use the curb, sidewalk and parking lot stripes to hint as to the correct location for scan #8.

scan8.png

After moving #8 to the correct position, tap the green checkmark to start the realignment process.

process.png

If the proposed realignment fails, the scan returns to its original position. If it succeeds, you can then proceed finishing that project and upload it for processing.

Example #2:

In this example, fixing a misaligned scan illustrates how dependent children are moved automatically. In the screenshot below, scan #12 should be between scans #6 and #7. Scan 28 has also landed on top of 27, which we’ll also fix, but not in this example.

1.png

Like in the first example, we start by selecting “Realign Scans” from the preview menu for scan #12 (not shown here for brevity).

As shown below, sliding #12 out to the left helps illustrate that not only does scan #12 need to slide up between #6 and #7, but it also needs to rotate about 90° clockwise for the green sections to match up. This fragment of the minimap acts like a puzzle piece, and you can use it to more accurately line up the suggested location.

 

2.png

Tap and slide #12 up, then using two fingers, rotate the scan approximately 90 degrees. The yellow lines shown here are the current primary alignment links for debugging purposes.

3.png

Move #12 into the right spot as shown below, sliding with one finger on the scan icon, or using two fingers to adjust rotation until the preview of the floor plan appears to line up. In this example the bright green sections make it easier to line up - this doesn’t have to be extremely precise. Tap the green check mark in the scan button to start the alignment process, using the new position as a suggestion.

4.png

In this case the realignment was successful - #12 is in now the correct position, and dependent scans #13-16 have also moved into the correct locations.5.png

Key requirements:

  • You can suggest a new position for any 3D scan except for the very first scan (#1), which is the anchor for the local coordinate system
  • This Beta feature is available on Android with Capture version 1.2 or higher
  • Coming soon to Capture on iOS

Basics, best practices:

    1. Slide and/or rotate: one finger on the scan marker to move, two fingers around the scan marker to rotate it
    2. Match surroundings: slide and rotate the scan, trying to match fragments from the scan to what you see in the bird’s eye preview of the minimap
  • Temporary floors: for dense, complex or large scans, it may be helpful to select a group of scans containing the misalignment and move them to a temporary floor. This may make it easier to visualize the problem, and you can attempt to realign within that temporary floor group, then move them back to the original floor. The alignment algorithm is constrained to a floor, so this may help constrain options in addition to the hint that you are providing by rotating and sliding the problematic scan.

Limitations, known issues:

  • This will not solve all alignment (misplaced scan) issues. Sometimes adding more scans in a troublesome area can help. Ensure reflecting wall surfaces such as mirrors are marked (or windows if it is dark outside and they are reflecting the interior). 
  • If the system selects a new location for the scan that is worse than before, try moving it via the Realign menu back to the prior location. There is currently no ‘undo’ option or confirmation to accept the new realigned location. Trying to move it back usually acts as an undo operation.

Feedback:

Please report issues, ask questions and make suggestions for improvements or new features to capture-beta@matterport.com.