Adding face IDs to geometry

Hello,

I am trying to create unique face IDs for my geometry for meshing, but to no success. Only one face can be identified (F1), instead of four, when you run the code below:

thermalmodelS = createpde('thermal','transient');

%Geometry definition

r1 = [3 4 -.17 .17 .17 -.17 -.17 -.17 .17 .17];

r2 = [3 4 -.15 .15 .15 -.15 -.15 -.15 .15 .15];

gdm = [r1; r2]';

g = decsg(gdm,'r1-r2',['r1'; 'r2']');

r2 = [3 4 -.15 .15 .15 -.15 -.15 -.15 .15 .15];

r3 = [3 4 -.09 .09 .09 -.09 -.09 -.09 .09 .09];

gdm = [r2; r3]';

g = decsg(gdm,'r2-r3',['r2'; 'r3']');

r3 = [3 4 -.09 .09 .09 -.09 -.09 -.09 .09 .09];

r4 = [3 4 -.07 .07 .07 -.07 -.07 -.07 .07 .07];

gdm = [r3; r4]';

g = decsg(gdm,'r3-r4',['r3'; 'r4']');

geometryFromEdges(thermalmodelS,gd);

pdegplot(thermalmodelS,'EdgeLabels','on','FaceLabels','on')

xlim([-0.25 0.25])

ylim([-0.2 0.2])

axis equal

Please help.

Answer 1

[Avni Agrawal]

Hi,

I understand that you are trying to identify 4 face ids and label them. It seems there might be a bit of confusion regarding the number of faces in a 2D square. While it's understandable to think that a square has four faces, in reality, a square in a 2D geometry actually has only one face.

In two-dimensional space, a face refers to a flat surface that encloses a shape. In the case of a square, all four sides of the square are connected, forming a single continuous boundary. This means that there is only one face that encompasses the entire square.

It's important to note that the concept of faces becomes more relevant in three-dimensional geometry, where objects can have multiple distinct faces. But in the context of a 2D square, there is only one face, which is the entire square itself.

Take a look at this document for further assistance:

https://in.mathworks.com/help/pde/ug/pde.discretegeometry.addface.html