%--------------------------
 % @Author: Jingqiao Hu
 % @Date: 2021-11-01 16:28:21
 % @LastEditTime: 2021-11-02 17:09:19
%--------------------------
function [iK, jK, edofMat, EleNodesID, iEner] = forAssemble_trimesh(faces)
    m = size(faces, 1);

    edofMat0 = [2*faces-1, 2*faces]; % [n,6], arranged as KE, for U(edofMat) * KE
    edofMat = edofMat0(:, [1,4,2,5,3,6]);

    iK = reshape(kron(edofMat,ones(6,1)).',36*m,1);
    jK = reshape(kron(edofMat,ones(1,6)).',36*m,1);

    EleNodesID = edofMat(:,2:2:6)./2; 
    iEner = EleNodesID'; 
end