FILT: Add filter to extract microstructure triple lines from surface meshes

CMakeLists.txt

@@ -608,6 +608,7 @@ set(SIMPLNX_HDRS
 
   ${SIMPLNX_SOURCE_DIR}/Utilities/Meshing/VertexUtilities.hpp
   ${SIMPLNX_SOURCE_DIR}/Utilities/Meshing/TriangleUtilities.hpp
+  ${SIMPLNX_SOURCE_DIR}/Utilities/Meshing/TripleLineUtilities.hpp
 
   ${SIMPLNX_SOURCE_DIR}/Utilities/Parsing/DREAM3D/Dream3dIO.hpp
   ${SIMPLNX_SOURCE_DIR}/Utilities/Parsing/DREAM3D/Dream3dPreflightCache.hpp
@@ -807,6 +808,7 @@ set(SIMPLNX_SRCS
 
   ${SIMPLNX_SOURCE_DIR}/Utilities/Meshing/VertexUtilities.cpp
   ${SIMPLNX_SOURCE_DIR}/Utilities/Meshing/TriangleUtilities.cpp
+  ${SIMPLNX_SOURCE_DIR}/Utilities/Meshing/TripleLineUtilities.cpp
 
   ${SIMPLNX_SOURCE_DIR}/Utilities/Parsing/DREAM3D/Dream3dIO.cpp
   ${SIMPLNX_SOURCE_DIR}/Utilities/Parsing/DREAM3D/Dream3dPreflightCache.cpp

src/Plugins/SimplnxCore/CMakeLists.txt

@@ -105,6 +105,7 @@ set(FilterList
   PadImageGeometryFilter
   PartitionGeometryFilter
   ExtractFeatureBoundaries2DFilter
+  ExtractTripleLinesFilter
   PointSampleEdgeGeometryFilter
   PointSampleTriangleGeometryFilter
   QuickSurfaceMeshFilter

src/Plugins/SimplnxCore/docs/ExtractTripleLinesFilter.md

@@ -0,0 +1,74 @@
+# Extract Triple Lines
+
+## Group (Subgroup)
+
+Surface Meshing (Generation)
+
+## Description
+
+This **Filter** extracts the *triple lines* of a multi-material surface mesh into a new **Edge Geometry**.
+
+A mesh edge is a triple line segment when the triangles that share it border **three or more distinct
+Feature Ids**. Where three grains meet, the segment borders three Feature Ids; where four meet, it
+borders four and forms a *quadruple point line*.
+
+Because the lines are extracted from whatever **Triangle Geometry** is supplied, they always lie exactly
+on that surface. This is the reason the extraction is a separate **Filter** rather than an option on the
+surface meshing filters: placing it *after* a smoothing step means the triple lines follow the smoothed
+surface.
+
+A typical pipeline is:
+
+1. **Quick Surface Mesh** (or **SurfaceNets**, or **M3C Surface Meshing**)
+2. **Laplacian Smoothing** on the Triangle Geometry
+3. **Extract Triple Lines**
+
+Running the extraction before smoothing instead simply yields the lines of the unsmoothed mesh.
+
+### Include Exterior Triple Lines
+
+The outside of the volume is represented in **Face Labels** by the value `-1`. *Include Exterior Triple
+Lines* controls whether that counts as a distinct region.
+
+When disabled (the default), only interior triple lines are produced. When enabled, a grain boundary
+that reaches the free surface of the volume also registers as a triple line, because the outside counts
+as a third region there. Enabling it therefore produces noticeably more segments.
+
+### Created Outputs
+
+The created **Edge Geometry** contains:
+
+| Output | Description |
+|--------|-------------|
+| Shared Vertex List | Only the vertices lying on a triple line, copied from the source mesh |
+| Shared Edge List | The triple line segments |
+| Number of Features | Per segment: `3` for a triple line, `4` for a quadruple point line |
+| Node Types | Per vertex, copied from the source mesh's **Node Types** |
+
+The vertex list is a compacted copy rather than a reference, so the **Edge Geometry** is self-contained:
+smoothing or deleting the source **Triangle Geometry** afterwards cannot corrupt it. The trade-off is
+that the triple lines will *not* follow the mesh if it is modified after extraction — re-run this
+**Filter** to bring them back into alignment.
+
+**Node Types** is copied through so that the created **Edge Geometry** can be used directly by filters
+that require a node type array, such as **Laplacian Smoothing**, which accepts Edge Geometries.
+
+## Notes
+
+The ordering of the created vertices and edges is deterministic for a given build but is not guaranteed
+to be identical across platforms. Comparisons against a stored exemplar should sort the edges and
+vertices first rather than relying on their order.
+
+% Auto generated parameter table will be inserted here
+
+## Example Pipelines
+
+## License & Copyright
+
+Please see the description file distributed with this **Plugin**
+
+## DREAM3D-NX Help
+
+If you need help, need to file a bug report or want to request a new feature, please head over to the
+[DREAM3DNX-Issues](https://github.com/BlueQuartzSoftware/DREAM3DNX-Issues/discussions) GitHub site where
+the community of DREAM3D-NX users can help answer your questions.