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Boolean

The Boolean tool executes geometric Boolean operations on surface meshes, computing the union, intersection, or difference between input surfaces. Boolean operations are fundamental for combining, subtracting, or finding common regions between 3D objects.

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​

Boolean operations treat surfaces as solid volumes and compute geometric relationships between them:

OperationResultFormulaUse Case
UnionCombined volume of both inputsA + BMerging overlapping structures
IntersectionCommon volume shared by both inputsA ∩ BFinding overlapping regions
DifferenceVolume of A with B removedA - BSubtracting one shape from another

Unlike the Merge tool which simply concatenates mesh data, Boolean operations compute the actual geometric relationship between the volumes, producing clean, manifold results.

Interface​

Boolean Operation​

Select the type of operation to perform:

OperationDescription
UnionCombine both inputs into a single volume (A + B)
IntersectionKeep only the overlapping region (A ∩ B)
DifferenceSubtract Input B from Input A (A - B)

Options​

OptionDescription
Input AThe first (primary) surface for the operation
Input BThe second surface(s) for the operation (can select multiple)
ResultTarget for the result (new surface or replace existing)

Boolean Operations Explained​

Union (A + B)​

Creates a single surface encompassing the combined volume of both inputs. Overlapping regions are merged, and internal geometry is removed.

Example uses:

  • Combining adjacent anatomical structures
  • Creating a unified mold from multiple parts
  • Merging segmented regions that should be treated as one

Intersection (A ∩ B)​

Creates a surface containing only the volume that is common to both inputs—the region where they overlap.

Example uses:

  • Finding the overlapping region between two structures
  • Identifying contact areas between objects
  • Creating interference detection results

Difference (A - B)​

Creates a surface that is Input A with the volume of Input B removed. The result is the portion of A that does not overlap with B.

Example uses:

  • Creating holes or cavities
  • Subtracting one structure from another
  • Carving out material for implant fitting
Order Matters for Difference

For the Difference operation, the order of inputs matters. A - B produces a different result than B - A. Make sure you select the correct surface as Input A (the one you want to keep).

Actions​

ButtonDescription
ApplyExecute the Boolean operation

Requirements​

For successful Boolean operations, input surfaces should be:

  1. Closed (watertight): No holes or open boundaries
  2. Manifold: Each edge shared by exactly two triangles
  3. Non-self-intersecting: No faces intersecting themselves

Use Diagnostics and Fixes to verify and repair surfaces before performing Boolean operations.

Typical Workflows​

Combining Two Structures​

To merge two overlapping surfaces into one:

  1. Open the Boolean tool
  2. Select Union operation
  3. Choose the first surface as Input A
  4. Choose the second surface as Input B
  5. Click Apply

Creating a Hole/Cavity​

To subtract one shape from another:

  1. Position the "tool" surface (the shape to subtract) where you want the hole
  2. Open the Boolean tool
  3. Select Difference operation
  4. Choose the main object as Input A
  5. Choose the tool shape as Input B
  6. Click Apply

Finding Overlapping Volume​

To identify where two surfaces overlap:

  1. Open the Boolean tool
  2. Select Intersection operation
  3. Choose both surfaces as Input A and Input B
  4. Click Apply

The result contains only the shared volume.

Complex Boolean Chains​

For complex operations involving multiple surfaces:

  1. Perform operations pairwise
  2. Use the result of one operation as input to the next
  3. Build up the final geometry incrementally

Boolean vs. Voxel Boolean​

AspectBooleanVoxel Boolean
AlgorithmGeometric mesh operationsVoxel-based conversion and operations
Input requirementsClean, manifold meshesMore tolerant of mesh issues
PrecisionHigh geometric precisionResolution-dependent
SpeedFast for simple cases, slow for complexConsistent performance
Best forClean, well-formed inputsProblematic or complex inputs

If the standard Boolean operation fails due to mesh quality issues, try Voxel Boolean as an alternative.

Troubleshooting​

Boolean Operation Fails​

If the operation doesn't produce expected results:

  1. Check mesh quality: Use Diagnostics and Fixes to verify both inputs are closed and manifold
  2. Fill holes: Use Fill Holes to close any open boundaries
  3. Try Voxel Boolean: For problematic meshes, Voxel Boolean may succeed where geometric Boolean fails
  4. Simplify inputs: Complex geometry may cause issues—try Reduce to simplify first

Unexpected Results​

If the result doesn't look right:

  1. Verify input selection: Ensure you selected the correct surfaces for A and B
  2. Check operation type: Confirm you chose the right operation (union vs. intersection vs. difference)
  3. Review normals: Inverted normals can cause incorrect results—use Diagnostics and Fixes to check
  4. Examine overlapping regions: Boolean operations require actual geometric overlap; touching or nearby surfaces may not produce expected results

Best Practices​

  1. Prepare inputs: Run Diagnostics and Fixes on both surfaces before Boolean operations.

  2. Save before operating: Boolean operations modify geometry significantly. Save your work or duplicate surfaces before proceeding.

  3. Start simple: Test operations on simple geometries first to understand the behavior.

  4. Use appropriate tool: For non-overlapping surfaces that just need combining, use Merge instead—it's faster and simpler.

  5. Verify results: After Boolean operations, run diagnostics to verify the result is manifold.

See Also​