Features of crack patterns are explored by performing computer simulations of crack growth in the two-dimensional model systems of triangular lattice. The simulations are concerned with crack growth in brittle materials to which the stain energy is supplied nonuniformly.It is shown that the present model gives different crack patterns and strain energy distributions, which are almost independent of the shape of lattice. The results of simulations have some implications in evaluating crack patterns in real materials which were exposed to thermal shock, radiation and so on; the differences in materials and external influences could be conjectured from the characteristic aspects of observed crack patterns.