Most of the researchers on watermarking techniques have focused on protecting the copyright information in various data such as audio, image and video signals. However, relatively less watermarking techniques are in respect of copyright protection of 3D model objects. After analyzing the data structure of 3D models, we propose a novel and efficient algorithm which allows embedding public watermarks containing copyright information into 3D models consisting entirely of triangle meshes. In the proposed algorithm, watermarks are embedded into a 3D model by altering model vertices with weights and along directions that are all adaptive to the local geometry. The geometrybased algorithm allows of higher robustness with transparency. Experimental results and the attack analysis demonstrate that the proposed watermarking algorithm is transparent and robust against the combination of various attacks.