Three-dimensional data reveals more explicative information and more realistic visualization than that of the two-dimensional ones. This explains the remarkable growth in the use of 3D data in different fields of application, which increases in respect to the risk of illegal use of data and piracy, as well. Since its appearance, digital watermarking has been an essential solution to attest the identity of the owner, control illegal reproduction, and protect the copyright of the 3D object. The current work is about designing a robust 3D object watermarking technique in order to protect copyrights associated with triangular polygon meshes. The approach is based on a watermark's insertion in the spatial domain. The findings are a proof demonstrating that the proposed 3D objects watermarking method does not only meet the need of imperceptibility but also shows, at least, similar or even better robustness, compared with other commonly used 3D objects watermarking approaches in the literature.