Add examples for fixed edges

README.md

@@ -160,6 +160,15 @@ via CSV files. This example shows an airfoil that has been meshed in this way.
 <img src="doc/airfoil.png" alt="TQMesh-airfoil" width="350"/>
 </details>
 
+
+<details>
+<summary>Fixed interior edges</summary>
+
+Fixed edges can be defined within the domain to guide the meshing process.
+
+<img src="doc/fixed_edges.png" alt="TQMesh-fixed-edges" width="350"/>
+</details>
+
 ## Output format
 Currently, **TQMesh** features the VTU output format (which can be read for example by Paraview) or alternatively a simple text output format.
 

input/09_fixed_interior_edges.para

@@ -1,13 +1,9 @@
 #===========================================================
 #                         TQMESH     
 #===========================================================
- 
+
 #-----------------------------------------------------------
 #                     MESH DEFINITION
-#
-# First, we provide some general meshing properties,
-# such as the overall element size, element color and 
-# the applied meshing algorithm:
 #-----------------------------------------------------------
 Define mesh:
   Element size: 0.35 
@@ -21,40 +17,45 @@ Define mesh:
   Output file prefix: ./fixed_edges
 
   #---------------------------------------------------------
-  #
+  #                        BOUNDARIES
   #---------------------------------------------------------
   Define boundary vertices:
-   1.0, 0.0
-   6.0, 0.5
-   4.0, 5.0
-  -1.0, 4.5
+   1.0, 0.0                 # Vertex 0
+   6.0, 0.5                 # Vertex 1
+   4.0, 5.0                 # Vertex 2
+  -1.0, 4.5                 # Vertex 3
   End boundary vertices
 
-  #---------------------------------------------------------
-  #
-  #---------------------------------------------------------
   Define exterior boundary edges:
-    0, 1,    2                 # 2: Color for bottom edge
-    1, 2,    3                 # 3: Color for right edge
-    2, 3,    2                 # 2: Color for top edge
-    3, 0,    1                 # 1: Color for left edge
+    0, 1, 1 
+    1, 2, 2 
+    2, 3, 3 
+    3, 0, 4 
   End exterior boundary edges
 
   #---------------------------------------------------------
+  #               FIXED VERTICES & FIXED EDGES
   #
+  # Similar to interior / exterior boundary edges, we define
+  # fixed edges by providing the IDs of the respective start
+  # and ending vertices. However, fixed vertices do not 
+  # require the additional color values. 
+  # Note, that the vertex ID count starts with boundary v
+  # vertices and proceeds with fixed vertices - as indicated 
+  # in the comments.
   #---------------------------------------------------------
   Define fixed vertices:
-     2.5, 2.5, 0.05, 1.0               # 4
-     1.5, 1.5, 0.05, 1.0
-     3.5, 1.5, 0.05, 1.0
-     3.5, 3.5, 0.05, 1.0
-     1.5, 3.5, 0.05, 1.0
+     2.5, 2.5, 0.05, 1.0    # Vertex 5
+     1.5, 1.5, 0.05, 1.0    # Vertex 6
+     3.5, 1.5, 0.05, 1.0    # Vertex 7
+     3.5, 3.5, 0.05, 1.0    # Vertex 8
+     1.5, 3.5, 0.05, 1.0    # Vertex 9
   End fixed vertices
 
   Define fixed edges:
-   4, 5
-   4, 6
-   4, 7
+   4, 5             # This edge connects vertex 4 and vertex 5,
+   4, 6             # this edge connects vertex 4 and vertex 6
+   4, 7             # and so on ...
    4, 8
    5, 6
    6, 7

src/examples/09_fixed_edges.cpp

@@ -0,0 +1,95 @@
+/*
+* This file is part of the TQMesh library.  
+* This code was written by Florian Setzwein in 2022, 
+* and is covered under the MIT License
+* Refer to the accompanying documentation for details
+* on usage and license.
+*/
+#include <iostream>
+#include <cassert>
+
+#include "TQMesh.h"
+#include "run_examples.h"
+
+using namespace CppUtils;
+using namespace TQMesh;
+/*********************************************************************
+* This example covers the usage of fixed interior edges
+*********************************************************************/
+bool fixed_edges()
+{
+  UserSizeFunction f = [](const Vec2d& p) { return 0.35; };
+
+  Domain domain { f };
+
+  // Vertices
+  Vertex& v0 = domain.add_vertex( 1.0,  0.0 ); 
+  Vertex& v1 = domain.add_vertex( 6.0,  0.5 ); 
+  Vertex& v2 = domain.add_vertex( 4.0,  5.0 );
+  Vertex& v3 = domain.add_vertex(-1.0,  4.5 );
+
+  Boundary&  b_ext = domain.add_exterior_boundary();
+  b_ext.add_edge( v0, v1, 1 ); // 1: Color for bottom edge
+  b_ext.add_edge( v1, v2, 2 ); // 2: Color for right edge
+  b_ext.add_edge( v2, v3, 3 ); // 3: Color for top edge
+  b_ext.add_edge( v3, v0, 4 ); // 4: Color for left edge
+
+  // Fixed vertices
+  Vertex& v4 = domain.add_fixed_vertex(2.5, 2.5, 0.05, 1.0);
+  Vertex& v5 = domain.add_fixed_vertex(1.5, 1.5, 0.05, 1.0);
+  Vertex& v6 = domain.add_fixed_vertex(3.5, 1.5, 0.05, 1.0);
+  Vertex& v7 = domain.add_fixed_vertex(3.5, 3.5, 0.05, 1.0);
+  Vertex& v8 = domain.add_fixed_vertex(1.5, 3.5, 0.05, 1.0);
+
+  // Define fixed edges 
+  domain.add_fixed_edge( v4, v5 );
+  domain.add_fixed_edge( v4, v6 );
+  domain.add_fixed_edge( v4, v7 );
+  domain.add_fixed_edge( v4, v8 );
+
+  domain.add_fixed_edge( v5, v6 );
+  domain.add_fixed_edge( v6, v7 );
+  domain.add_fixed_edge( v7, v8 );
+  domain.add_fixed_edge( v8, v5 );
+
+  /*------------------------------------------------------------------
+  | Mesh generation 
+  ------------------------------------------------------------------*/
+  MeshGenerator generator {};
+  Mesh& mesh = generator.new_mesh( domain );
+
+  generator.triangulation(mesh).generate_elements();
+
+  generator.quad_refinement(mesh).refine();
+
+  generator.mixed_smoothing(mesh)
+    .epsilon(0.7) 
+    .smooth(5);  
+
+  /*------------------------------------------------------------------
+  | Check if the meshing generation process succeeded
+  ------------------------------------------------------------------*/
+  MeshChecker checker { mesh, domain };
+  if ( !checker.check_completeness() )
+  {
+    LOG(ERROR) << "Mesh generation failed";
+    return false;
+  }
+
+  /*------------------------------------------------------------------
+  | Finally, we export the mesh to a file in VTU / TXT format.
+  ------------------------------------------------------------------*/
+  std::string source_dir { TQMESH_SOURCE_DIR };
+  std::string file_name 
+  { source_dir + "/auxiliary/example_data/fixed_edges" };
+
+  LOG(INFO) << "Writing mesh output to: " << file_name << ".vtu";
+  generator.write_mesh(mesh, file_name, MeshExportType::VTU );
+
+  LOG(INFO) << "Writing mesh output to: " << file_name << ".txt";
+  generator.write_mesh(mesh, file_name, MeshExportType::TXT );
+
+
+  return true;
+
+} // fixed_edges()

src/examples/CMakeLists.txt

@@ -4,7 +4,8 @@ add_executable( ${EXAMPLES}
   #example_9.cpp
   #example_8.cpp
   #example_7.cpp
-  09_tqmesh_banner.cpp
+  10_tqmesh_banner.cpp
+  09_fixed_edges.cpp
   08_thin_fracture.cpp
   07_multiple_meshes.cpp
   06_airfoil_from_csv.cpp

src/examples/run_examples.cpp

@@ -96,6 +96,13 @@ int run_examples(const std::string& example)
     success &= thin_fracture();
   } 
   else if ( !example.compare("9") || !example.compare("09") ||
+            !example.compare("fixed_edges") )
+  {
+    LOG(INFO) << "Running example \"fixed_edges\"...";
+    LOG(INFO) << "";
+    success &= fixed_edges();
+  } 
+  else if ( !example.compare("10") ||
             !example.compare("tqmesh_banner") )
   {
     LOG(INFO) << "Running example \"tqmesh_banner\"...";

src/examples/run_examples.h

@@ -26,6 +26,7 @@ bool merge_meshes();
 bool airfoil_from_csv();
 bool multiple_meshes();
 bool thin_fracture();
+bool fixed_edges();
 bool tqmesh_banner();
 bool run_example_7();
 bool run_example_8();