Last week, I shared some tips about Automatic Alignment. Many users were also curious about Manual Multi-Project Alignment and how it works.
So today, I’d like to share the principles behind this feature and some tips for achieving better alignment results.
Manual Alignment requires users to select at least 3 corresponding points from each scan project. These points can be selected from either markers or geometric features. Markers provide clearer and more precise references, making it easier to select the corresponding points and achieve more reliable alignment results.
With at least 3 non-collinear corresponding points, the software can determine the spatial relationship (position and orientation) between two scan projects.
Based on these 3 points, the software will:
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Determine the relative positional relationship between the two projects.
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Calculate the required rotation and translation, and then align the two projects.
However, the 3 selected points only provide an initial alignment. The software will further optimize the result based on the overlapping areas, searching for the position with the lowest overall alignment error. Therefore, the final alignment may shift if the overlapping area lacks sufficient geometric information.
Manual Alignment can become challenging when:
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The selected 3 points are not the same physical locations in both projects, especially with repetitive or symmetrical structures.
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The 3 points are not distributed widely enough to provide sufficient spatial constraints, or they are arranged in a straight line.
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The selected areas lack unique geometric features, such as large flat surfaces or smooth curved surfaces, which may affect the optimization result.
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The overlapping area between the two projects is insufficient.
Tips for Better Manual Alignment Results:
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Select the same physical locations in both scan projects.
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Distribute the 3 points across a larger area. Avoid placing them too close together or along the same line.
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Choose areas with clear geometric features, such as edges, corners, or areas with obvious height variations.
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Prepare sufficiently before scanning, making sure there are enough overlapping areas and features.
Have you used Manual Alignment before? Share your scanning results or alignment tips with us!
