Create Edges
Use Create Edges () to create edges in a mesh by clicking on mesh edges in the graphics or by selecting existing points, as shown in Figure 8-45. It is possible to add a Create Edges node when the mesh sequence includes either an Import node or a Create Vertices node.
Figure 8-45: Clicking in the Graphics window to select mesh edges to convert into geometric edges (left). Connecting two selected points of an imported STL mesh with a meshed edge (right).
Note that creating edges can modify the number of geometric edges in the mesh. Thus, when you are adding this operation to a meshing sequence that is conforming with the component’s geometry, a new meshing sequence that is defining its own geometric model is automatically created, and the Create Edges node is added to this new sequence. For more information, see The Mesh Node.
To add a Create Edges node, choose one of the following:
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For a 3D mesh, it is available from the Create Entities menu () on The Mesh Toolbar. For 2D meshes, click the Create Edges () button directly in the Mesh toolbar.
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Right-click the Mesh node and select Create Edges (). In 3D, do this from the Create Entities menu.
Choose between creating new meshed edges between vertices or converting existing mesh edges into edge elements. Edges between vertices can be created in empty space but also overlap existing mesh. Such an edge will not partition existing mesh elements. In 3D, it is possible to Imprint an edge on a boundary to partition the boundary elements with the edge. To partition a domain in 2D with a straight line, use Intersect with Line.
Edge Specification
From the Specify list, select Mesh edges (default) to convert mesh edges to edge elements. This is done by clicking on mesh edges in the Graphics window. Alternatively, choose Vertices to specify the positions of start and end vertices.
Mesh Edge Selection
Click the Active button to toggle between turning ON and OFF the mesh edge selection. This enables selection by clicking in the Graphics window. When the Active button is toggled ON, the Mesh Rendering will automatically be turned ON to facilitate the selection of vertices. Select a mesh edge to populate the table with the x-, y-, and (3D only) z-coordinates of the midpoint of the mesh edge. It is possible enter the exact x-, y-, and (3D only) z-coordinates manually in the table. Selected edges are highlighted in the Graphics. Click a second time on the same edge to remove it from the selection.
If you specify mesh edges by providing a list of coordinates, and later modify the input mesh, the list of selected coordinates is updated to match the new mesh, if possible.
It is only possible to select mesh edges on boundaries in 3D which are visible in the Graphics window. Use Click and Hide and the clipping tools to get access to interior boundaries. Rotate the mesh to make the opposite side come into view.
Starting Vertices, End Vertices
To create edges, select vertices in the Starting Vertices and End Vertices sections. Edges will be created from vertices in the selection in Starting Vertices to vertices in the selection in End Vertices. From each vertex in the selection in Starting Vertices, edges will be created to the closest vertices in the selection in End Vertices.
Element Size
To specify the size distribution of the edge mesh, select one of the methods from the Size distribution type list:
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Select Element size (the default) to specify the maximum element size (SI unit: m), which you enter in the Maximum element size field. The value is a relative number (default: 0.1 in 3D and 1/15 in 2D). This value is multiplied with the size of the bounding box.
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Select Fixed number of elements to use a fixed number of mesh elements, which you enter into the Number of elements field (default: 1).
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Select Explicit distribution to use an explicit, user-defined element distribution. To define the distribution of mesh elements, enter a vector-valued expression defining a strictly increasing sequence of nonnegative numbers (using comma-separated numbers) in the Relative placement of vertices along edge field, specifying the relative arc length values of the mesh vertices along the edge or boundary. Select the Reverse direction check box to reverse the direction of the explicit distribution.
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Select Predefined distribution to specify properties of a predefined distribution method where the element size can be exponentially or linearly increasing or decreasing. From the Growth rate list, select Exponential to let the distribution method be a geometric sequence and Linear for an arithmetic sequence. In addition, specify values in the Number of elements and Element ratio fields to determine the number and ratio of elements in the distribution. Select the Symmetric distribution check box to make the predefined size distribution symmetric. Select the Reverse direction check box to reverse the direction of the predefined distribution.
Selections of Resulting Entities
Select the Resulting domains check box to create a predefined selection in subsequent nodes in the mesh sequence. To also make the selection available in all applicable selection lists outside the mesh sequence or mesh part (in physics and materials settings, for example), select the Show in physics (Show outside part if in a mesh part) check box. These selections do not appear as separate selection nodes in the model tree.
See STL Import 1 — Generating a Geometry from an Imported Mesh: Application Library path COMSOL_Multiphysics/Meshing_Tutorials/stl_vertebra_import.
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Create Faces
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Create Vertices