Computes the shape function derivatives and the determinant for of 1D linear isoparametric elements. This function is used internally from shapeDerivatives.
Version : 1.0
Author : George Kourakos
Department of Land Air and Water
University of California Davis
[B Jdet]=shapeDerivLine_Lin(p, MSH, n)
p: [Np x 3] Coodrinates of nodes [x1 y1 z1; x2 y2 z2;...xn yn zn], where Np is the number of nodes
MSH: [Nel x Np_el] id of elements. Each row correspond to an element. Nel is the number of elements and Np_el is the number of nodes to define the element
n: the integration point where the derivatives will be evaluated. For linear line elements this is empty because the derivative is constant.
B: Shape function derivatives
Jdet: The determinant of the Jacobian Matrix
N1 = 0.5 * (1 - xi)
N2 = 0.5 * (1 + xi)
dN1 = -1/2;
dN2 = 1/2;