ABSTRACT: In the field of practical rock engineering, there are two independent computations: continuous computation and limit equilibrium computation. Limit equilibrium is still the fundamental method for global stability analysis. For any numerical method in rock engineering, reaching limit equilibrium requires large displacements, discontinuous contacts, precise friction law, multi-step computation and stabilized timestep dynamic computation. Therefore three convergences are unavoidable: convergence of equilibrium equations, convergence of open-close iterations for contacts and convergence of the contact forces of dynamic computations. This paper will cover key block theory, two dimensional Discontinuous Deformation Analysis (DDA), three dimensional joint cutting and a simple version of three dimensional DDA.