Illustrate how to use function mp_edge_relations

Create Mesher object
Set meshing parameters
Create object describing geometric model
Show mesh
Edge data in elements
Create edges selector
Get edges data in regions
Visualization normal and tangent vectors at nodes of the region edges with tag 2

Create Mesher object

When Mesher object is created it takes care of initializing interface to GMSH mesh generator

mesher = mp.Mesher();

Set meshing parameters

mesher.basename ='demolshape';
mesher.folder = '.';
mesher.dim = 2;
mesher.clean = true;
mesher.quadsonly = false;

Create object describing geometric model

geom = mp.geoms.LShapeGeom('my_domain');
geom.params.dW = 3;
geom.params.dt = 1.2;

% Generate and visualize mesh again.
mesh = mesher.generate(geom, struct('lc', 0.8));

Show mesh

viewer = mp.Viewer();
viewer.show(mesh);

Edge data in elements

Caclulate edge flags, edge tangent vector and edge normal vector for each element

Create edges selector

The LShapeGeom geometric model distinguishes boundary endges as well as their subsets. Here we prepare selector that will assign tag 0 to boundary edges, and tags 1 and 2 respectively to 'bottom' left' set.

selector.left = 1;
selector.bottom = 3;
selector.other = 4;
selector.boundary = 8;

% The use of Tagger is optional. Tagger object give the ability to precisely
% specify which tags are assigned if mesh elements belongs to multile
% regions. If one is not interested in such fine control it is enough to
% use 'default' string in place of tagger argument.
tagger = mp.Tagger('priority', [0,0; 1, 100; 2,50; 3,25;8,15]);

Get edges data in regions

[elemEdgeTags, elemTan, elemNor, nodeTan, nodeNor] = mp_face_edge_data_at_regions(mesh, 8, selector, tagger);

Visualization normal and tangent vectors at nodes of the region edges with tag 2

% Plot arrows for tangent and normal vectors
hold on;
quiver(mesh.nodes(:,1), mesh.nodes(:,2), nodeTan(:,1), nodeTan(:,2), 0.3, 'LineWidth', 1, 'Color', 'red');
quiver(mesh.nodes(:,1), mesh.nodes(:,2), nodeNor(:,1), nodeNor(:,2), 0.3, 'LineWidth', 1, 'Color', 'blue');

mp_manage_demos('report', 'mp_face_edge_data_at_regions', true);