Method calculate

SRC/element/shell/ASDShellQ4.cpp:217–234

        double detJ = 0.0;

        void calculate(const ASDShellQ4LocalCoordinateSystem& CS, const Matrix& dN)
        {
            // jacobian
            J(0, 0) = dN(0, 0) * CS.X1() + dN(1, 0) * CS.X2() + dN(2, 0) * CS.X3() + dN(3, 0) * CS.X4();
            J(1, 0) = dN(0, 0) * CS.Y1() + dN(1, 0) * CS.Y2() + dN(2, 0) * CS.Y3() + dN(3, 0) * CS.Y4();
            J(0, 1) = dN(0, 1) * CS.X1() + dN(1, 1) * CS.X2() + dN(2, 1) * CS.X3() + dN(3, 1) * CS.X4();
            J(1, 1) = dN(0, 1) * CS.Y1() + dN(1, 1) * CS.Y2() + dN(2, 1) * CS.Y3() + dN(3, 1) * CS.Y4();

            // determinant
            detJ = J(0, 0) * J(1, 1) - J(1, 0) * J(0, 1);
            double mult = 1.0 / detJ;

            // inv(jacobian)
            invJ(0, 0) = J(1, 1) * mult;
            invJ(1, 1) = J(0, 0) * mult;
            invJ(0, 1) = -J(0, 1) * mult;
            invJ(1, 0) = -J(1, 0) * mult;
        }
    
    };