A point sampling algorithm for 3D matching of irregular geometries

We present a 3D mesh re-sampling algorithm, carefully tailored for 3D object detection using point pair features (PPF). Computing a sparse representation of objects is critical for the success of state-of-the-art object detection, recognition and pose estimation methods. Yet, sparsity needs to preserve fidelity. To this end, we develop a simple, yet very effective point sampling strategy for detection of any CAD model through geometric hashing. Our approach relies on rendering the object coordinates from a set of views evenly distributed on a sphere. Actual sampling takes place on 2D domain over these renderings; the resulting samples are efficiently merged in 3D with the aid of a special voxel structure and relaxed with Lloyd iterations. The generated vertices are not concentrated only on critical points, as in many keypoint extraction algorithms, and there is even spacing between selected vertices. This is valuable for quantization based detection methods, such as geometric hashing of point pair features. The algorithm is fast and can easily handle the elongated/acute triangles and sharp edges typically existent in industrial CAD models, while automatically pruning the invisible structures. We do not introduce structural changes such as smoothing or interpolation and sample the normals on the original CAD model, achieving the maximum fidelity. We demonstrate the strength of this approach on 3D object detection in comparison to similar sampling algorithms.