Exctract specific triangles in a mesh

Consider the following mesh

This one was obtained using the PDE modeler app, from PDE toolbox. I need to extract all the triangles inside the square with a red edge, but I am not sure how to do it. Please any help will be appreciated

Answer 1

[Anurag]

Hi Diego,

I understand that you want extract specific triangles from a mesh, please refer to the following code which for a sample data does the same. The algorithm followed here is checking each triangle and keeping a track of those triangles which are inside the specified region.

% Sample mesh data

vertices = [
0, 0;
1, 0;
0, 1;
1, 1;
0.3, 0.3;
0.7, 0.3;
0.7, 0.7;
0.3, 0.7
];



faces = [
1, 2, 3;
2, 3, 4;
5, 6, 7;
7, 8, 5
];



% Sample square vertices

squareVertices = [
0.2, 0.2;
0.8, 0.2;
0.8, 0.8;
0.2, 0.8
];



% Initialize an array to store triangles inside the square
trianglesInsideSquare = [];



% Iterate through each triangle

for i = 1:size(faces, 1)
    % Get the vertices of the current triangle
    currentTriangle = vertices(faces(i, :), :);   
    % Check if all three vertices of the triangle are inside the square
    if all(inpolygon(currentTriangle(:, 1), currentTriangle(:, 2), squareVertices(:, 1), squareVertices(:, 2)))
        trianglesInsideSquare = [trianglesInsideSquare; faces(i, :)];      
    end
end

% Display the indices of triangles inside the square
disp('Indices of triangles inside the square:');
disp(trianglesInsideSquare);  

Hope this helped.

Regards,

Anurag