USER MANUAL

In many cases it is impossible to scan an object in one go. It may be due to its large size or because it has to be scanned from different sides and has to be flipped at some point. In such cases, several scans of the object are made and then combined to create a 3D model. It is important for these separate scans to overlap in order for them to be merged together in a consistent way.

Before merging a group of scans, they all have to be processed separately as described in Chapter 8: Post-Processing a Scan. Open the scans, register them, mark priority areas and finalize. Make sure that all separate scans look good. If some of the scans have noticeable defects, it is usually better to rescan corresponding areas. Poorly scanned zones may potentially spoil the entire model.

Since all the fragments were scanned separately, their position in respect to each other will be random. After all separate scans are processed, it is time to align them.

To start the alignment, select the scans needed to be aligned. After that, click  Align by Points button or press A. For this button to appear, all selected scans should contain valid results:

The alignment mode will be activated. There are four sections in the alignment window:

1. Meshes for Alignment. It is a list of all the results needed to be aligned. One of them is marked as Base.

2. Base is a stationary scan, in respect to which all other scans will be oriented.

3. Align is a scan that is currently being aligned to the Base.

4. Preview section shows how Base and Aligned scans are positioned in relation to one another.

To align a scan with the Base, pick a scan from the list. It will appear in the Align section.

If it is more convenient to place the scans one under another instead of side by side, it is possible to do with the Align Layout button, which allows to toggle between vertical and horizontal views of Align window. Also, the list of Meshes for Alignment can be detached by grabbing it by its header and placing it in any other convenient place on the screen.

To align a scan with the base, specify at least three points that this scan and the Base have in common. It is better to pick easily identifiable spots as common points. There is no need to be very precise. These are just reference points. To set a point, double click on the desired spot. To move the point, hold ctrl while drag it. Double-click the point to remove it. Set the same points on both the Base and the Aligned. Keep in mind that the sequence matters: if the points are the same, but their numbers differ on the Base and on a scan — the alignment will not be correct. Also:

• Do not put point too close to each other;

• Do not put points along the same line;

• Do not put points too close to the fringes of scans.

After a third point is selected on both the Base and the Aligned, the Preview will change. It will continue changing with each next point selected, but there is rarely a need to pick more than three or four points.

When a scan is aligned with the Base as necessary, press Add Aligned to Base. It runs best-fit algorithm, that finds the best possible position for aligned scan.

After Add Aligned to Base command is completed, the aligned scan will disappear from the list and Base will be shown as a sum of all aligned scans. Choose next scan to align and repeat the procedure. If all scans are added to the base, click Accept changes (or press Ctrl+F) to save new orientations of scans. If Cancel is clicked, the alignment will not be changed.

After alignment is complete, all aligned scans may look merged, but they are still separate scans:

It is vital to understand that "aligned" does not mean "combined". To merge all the scans into a final model, multiprocessing should be run. The idea is the same as with single scan processing: registration and finalization should be run, but this time a group of scans will be processed as one. To process selected scans as a single dataset, use Multiple Registration and Multiple Finalization.

A special case is an alignment of scans made in Marker Tracking Mode. If following conditions are met, such scans can be aligned without specifying common points (markers themselves will be used for this purpose):

• Marker positions should not be changed during the entire scanning session

• Scans marked for alignment should have reasonable amount of common markers (usually ten or more)

• If some of the markers were placed near the object and the object was moved or flipped between making separate scans, these additional markers should be either deleted or marked as irrelevant using Priority Mode tools. 

After selection of Base scan, just pick another scan that has enough overlap with the Base and click Add Aligned to Base. Adding common points is unnecessary, but still possible. The main condition here is a healthy amount of common markers (overlap) between Base and aligned scan. After marker-based alignment is complete, pick another scan and repeat the procedure.

If some of the scans made with Marker Tracking and some with Geometry Tracking or Texture Tracking, they still can be aligned. Use marker-based or point-based alignment for marker scans and point-based alignment for geometry or texture scans.

After marker-based alignment scans still need to undergo multiple processing to get the final result.

After an alignment is complete and all the results are positioned properly, Multiple Registration can be run. It uses separate point clouds as a single data set and analyses it to achieve the most cohesive and precise result possible. 

There are several ways of starting Multiple Registration:

• Long-press Start Multiple Non-Textured button and select Multiple Registration from the drop-down menu

• Right-click Start Multiple Non-Textured button and select Multiple Registration from the drop-down menu

• Press Ctrl+Shift+1 hotkey shortcut (hotkey can be changed in Settings if needed)

• Go to Files —> Start —> Stages (Multiple) —> Multiple Registration

• Press Multiple Registration button on Process Stages panel (This panel is hidden by default. Right-click Main Toolbar and pick Process Stages to see it.)

• Press Start Multiple Non-Textured button to run Multiple Registration and Multiple Finalization in sequence

• Press Ctrl+F5 to run Multiple Registration and Multiple Finalization in sequence

During Multiple Registration frames of each selected scan will be slightly adjusted to better fit frames of other scans. Because of that, previous results will no longer correspond to their respective point clouds and will be marked as invalid: the circle representing them will change color to brown and the names will be marked with asterisks. Plus, since there are no valid results, the preview of each selected scan will be shown, making irrelevant areas visible again as semi-transparent areas (parts of a table are seen on the example below): 

As with finalization of separate scans, Multiple Finalization generates a polygonal mesh based on a point cloud and finalization parameters chosen in Settings. The difference, of course, is that Multiple Finalization uses several point clouds from selected scans as a single data set, thus creating a combined final result. 

Select the scans needed to be merged, check the Settings (as described in Chapter 8), and then run Multiple Finalization:

• Long-press Start Multiple Non-Textured button and select Multiple Finalization from the drop-down menu

• Right-click Start Multiple Non-Textured button and select Multiple Finalization from the drop-down menu

• Press Ctrl+Shift+2 hotkey shortcut (hotkey can be changed in Settings if needed)

• Go to Files —> Start —> Stages (Multiple) —> Multiple Finalization

• Press Multiple Finalization button on Process Stages panel (This panel is hidden by default. Right-click Main Toolbar and pick Process Stages to see it.)

• Press Start Multiple Non-Textured button to run Multiple Registration and Multiple Finalization in sequence

• Press Ctrl+F5 to run Multiple Registration and Multiple Finalization in sequence

After Multiple Finalization is complete, the result will be shown as a separate project, marked with green Result label:

The result can then be edited with the tools Nest provides, such as hole-filling, bridging, smoothing, simplification, remeshing, filtering and others. These tools are covered in more detail in Chapter 10: Tools and Toolbars.

Starting from Calibry Nest 3.7.42, the result context menu includes a new option: Select Sources. Right-click a result and choose Select Sources to highlight all the scans that contributed to it:

Texturing a final model made of several scans is analogous to texturing a single-scan result: select the result to texturize and click Texturing button or press F6. If the model is comprised of more than 700 000 polygons, the prompt will appear suggesting simplifying the model before texturing. It is possible to decline this suggestion and texturize the model without simplifying it, but it may take an excessive amount of time to complete without returning much in terms of quality. Than is why it is recommended to simplify the model.

The original model will be preserved and another copy will be made for simplification and texturing. It will appear below the last result as a green circle with a random name with (textured) added to it:

After that, texture may be edited using texture editing tools: Adjust Texture, Luminosity Brush, Magic Clone Stamp. These tools are described in Chapter 10: Tools and Toolbars.

Saving the model made of separate scans is analogous to saving a single-scan result: right-click it and pick Save as..., then choose a path, a name and a format for the model. These results can be saved as .obj, .stl, .ply, .3mf or .wrl. Texture can only be saved in the .obj and .3mf formats. If saved in other formats, the model texture will be discarded.

It may also be useful to save all the scans with all the changes to a separate folder, in case there will be a need to reassemble the model with other parameters. Select all the scans needed to be saved, right-click on one of their names and pick Save Project As..., after which select a folder to save all selected processed scans.