We propose a robust 3D model watermarking scheme based on distributing the information corresponds to a bit of the watermark over the entire model via vertex scrambling. The scheme also adaptively varies the strength of the watermark signal with reference to the local geometry and embeds watermark information into the model by modifying the length of the vectors that link vertices to the centre of the model. Experiments show that this watermarking scheme is robust against attacks such as mesh simplification, addition of noise, and model cropping.