Merge

The Merge tool combines multiple surface objects into a single, unified surface object. This is useful for consolidating related components, simplifying the object tree, or preparing surfaces for operations that require a single input object.

Medical Disclaimer

This tool is provided for research and educational purposes only. Any clinical or diagnostic use requires proper validation in accordance with applicable regulations.

Overview

When you have multiple surface objects that represent parts of the same structure—such as separate bones that should be treated as a single skeletal region, or components that were split for editing—the Merge tool allows you to combine them efficiently.

The merge operation concatenates the mesh data from all selected surfaces into one object. Unlike Boolean Union, the Merge tool does not compute intersections or modify the geometry—it simply combines the vertex and triangle data.

Interface

Input Surfaces

Select the surface objects to merge. You can select multiple surfaces from the object tree or use the surface selector to pick visible surfaces.

Result

Specify the target for the merged result:

• New Surface: Create a new surface object containing the merged data
• Existing Surface: Replace an existing surface object with the merged result

Options

Option	Description	Default
Merge duplicate points	Remove duplicate vertices at the same location	Disabled
Remove input objects	Delete the original surface objects after merging	Disabled

Parameters

Merge Duplicate Points

When enabled, vertices that occupy the same spatial location (within a small tolerance) are merged into a single vertex. This is useful when:

• Merging surfaces that share common boundaries
• Combining components that were previously split
• Preparing surfaces for smoothing operations that need connected geometry

When disabled, all vertices are preserved as-is, which may result in coincident but disconnected vertices.

Remove Input Objects

When enabled, the original surface objects are automatically deleted after the merge operation completes successfully. This helps keep the object tree clean when you no longer need the individual components.

When disabled, both the merged result and the original surfaces are retained.

Actions

Button	Description
Apply	Perform the merge operation

Merge vs. Boolean Union

Understanding when to use Merge versus Boolean Union:

Scenario	Use Merge	Use Boolean Union
Surfaces don't overlap	✓	✓
Surfaces overlap and you want to compute the union		✓
You need to preserve internal structures	✓
Speed is critical	✓
Result must be manifold		✓

Merge:

• Fast operation (no geometry computation)
• Preserves all original triangles
• May result in overlapping or intersecting geometry
• Useful for grouping related components

Boolean Union:

• Computes the geometric union of volumes
• Removes internal/overlapping geometry
• Produces manifold result (when inputs are manifold)
• More computationally expensive

Typical Workflows

Consolidating Anatomical Structures

When segmenting complex anatomy, you might create separate masks for different parts:

1. Generate surfaces from individual segmentation masks
2. Select all related surfaces (e.g., all vertebrae of the spine)
3. Use Merge to combine them into a single surface object
4. Enable Remove input objects to clean up the object tree

Reassembling Split Surfaces

After using the Split tool or Editor to separate parts of a surface:

1. Make any necessary edits to the individual components
2. Select the surfaces to reassemble
3. Enable Merge duplicate points to reconnect shared boundaries
4. Apply the merge operation
5. Optionally use Smooth to blend the junction

Preparing for Export

When exporting to formats that support only a single mesh:

1. Select all surfaces to include in the export
2. Merge them into a single surface object
3. Run Diagnostics and Fixes if needed
4. Export the merged result

Best Practices

1. Check for overlaps: If merged surfaces overlap significantly, consider using Boolean Union instead, or run diagnostics afterward.

2. Enable duplicate point merging when appropriate: If surfaces share common boundaries and should form continuous geometry, enable this option.

3. Organize before merging: Ensure you're merging the correct surfaces. Consider renaming surfaces clearly before merging.

4. Keep originals for complex operations: If you're unsure about the result, leave Remove input objects disabled until you verify the merge was successful.

5. Run diagnostics after merging: Merged surfaces may contain issues like intersecting triangles. Use Diagnostics and Fixes to verify mesh quality.

See Also

• Boolean - Compute Boolean operations (union, intersection, difference)
• Split - Separate surface shells into individual objects
• Diagnostics and Fixes - Verify and repair mesh quality
• Filter Shells - Remove unwanted shells from a surface