This function finds the determinant of the jacobian and deformation matrix (B) of eight nodes brick element in finite element analysis:

function [J_det, B]=brick8(V,r,s,t)

%Input
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V: (8*3) Vertices coordinate matrix. The rows represent each node and columns x-coordinate ,y-coordinate and z-coordinate.
r,s and t: Values of natural coordinates at the location of integration point.

Output:
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J_det: Determinant of the jacobian
B: Deformation Matrix