Errors tolerance is a very important problem in simplifying triangulated surface model.An effective method to find tolerance errors is to use the whole inner and outer envelopes of a triangulated surface model.However

there will be many complicated operations to compute intersections between triangulations when constructing the whole inner and outer envelope of a triangulated surface model

which will lower the algorithm efficiency.We introduce a novel algorithm for simplifying triangulated surfaces model using the part offset-patches as errors tolerance

which are constructed by offsetting a part of triangles on the surface and can also be regarded as a small part of the whole inner and outer envelopes.Because the part offset-patches are much smaller than the whole inner and outer envelopes of a triangulated surface model

our algorithm is both simple and easy to implement.We also have developed a software system to test our algorithm.Experiment results show expense of our algorithm is much less than that in the algorithm using the whole inner and outer envelope of a triangulated surface model and it keeps higher similarity between simplified model and original one.