Algorithms have been developed for warping analysis and calculation of the shearing stresses in a general porous cross section of a long rod when it is subjected to twisting torques at its ends. The shape and dimensions of the cross section full of holes are defined from the binary segmented image data with by a micro-CT scanning technique. Finite difference approximation of the Laplace equation governing the cross-sectional warping leading to the matrix solution by a Gauss-Seidel process is discussed. Method of pointer matrix which keeps the locations of the nonzero elements of the coefficient matrix, is employed to expedite the iterative solution. Computer programs are coded in QuickBASIC language to facilitate plotting of the computed distributions of warping and shearing stresses. The classical torsional problem of square and thin-walled cross sections are used to reexamine the accuracy of the developed algorithms and results are found to be in very good agreement.