  This paper is a generalization of the previous work (Yang et.al, J. Comput.
Phys. 330 (2017), 863-883) to the 3-D irregular convex domains. The analytical
calculation formula of fractional derivatives of finite element basis functions
are given and a path searching method is developed to find the integration
paths corresponding to the Gaussian points. Moreover, a template matrix is
introduced to speed up the procedures. Numerical experiments on a steady
problem are presented verifying the efficiency of proposed techniques.
