Abstract: In order to help designers to check model changes quickly in a collaborative design, this
paper focuses on how to rapidly compare geometric differences between two 3D models. First, the
equidistant point clouds of two models are computed, and then a reference coordinate system of each
point cloud is obtained by using the principal component analysis method. A transformation is then
found to match the two point clouds to achieve an initial registration. Finally, the ICP (iterative
closest point) method is used to realize accurate registration for the two point clouds. By computing
the non-overlapping domain after the exact registration, we obtain the geometric differences between
the two point clouds. The numerical example shows that the proposed method can effectively
recognize the geometric differences of two 3D models.

Key words: point cloud, geometric registration, geometric comparison, collaborative modeling