An ab initio potential energy surface for the six-atom reaction CH3 + H-2 --> CH4 + H was constructed, within C-3v symmetry, by a modified Shepard interpolation method proposed recently by Collins et al. Selection of data points for the description of the potential energy surface was performed using both the Collins method and the dynamic reaction path (DRP) method. Although the DRP method is computationally more expensive, additional data points can be determined by just one simulation. Analyses of distributions of the data points, reaction probability, and errors in energy and energy gradients determined by the two different methods suggest a slight advantage for the DRP sampling in comparison with the iterative sampling.