Visual Quality Assessment of Point Clouds Compared to Natural Reference Images

This paper proposes a point cloud (PC) visual quality assessment (VQA) framework that reflects the human visual system (HVS). The proposed framework compares natural images acquired using a digital camera and PC images generated via 2D projection in terms of appropriate objective quality evaluation metrics. Humans primarily consume natural images; thus, human knowledge is typically formed from natural images. Thus, natural images can be more reliable reference data than PC data. The proposed framework performs an image alignment process based on feature matching and image warping to use the natural images as a reference which enhances the similarities of the acquired natural and corresponding PC images. The framework facilitates identifying which objective VQA metrics can be used to reflect the HVS effectively. We constructed a database of natural images and three PC image qualities, and objective and subjective VQAs were con- ducted. The experimental result demonstrates that the acceptable consistency among different PC qualities appears in the metrics that compare the global structural similarity of images. We found that the SSIM, MAD, and GMSD achieved remarkable Spearman rank-order correlation coefficient scores of 0.882, 0.871, and 0.930, respectively. Thus, the proposed framework can reflect the HVS by comparing the global structural similarity between PC and natural reference images.