Structure-aware viewpoint selection for volume visualization

Viewpoint selection is becoming a useful part in the volume visualization pipeline, as it further improves the efficiency of data understanding by providing representative viewpoints. We present two structure-aware view descriptors, which are the shape view descriptor and the detail view descriptor, to select the optimal viewpoint with the maximum amount of the structural information. These two proposed structure-aware view descriptors are both based on the gradient direction, as the gradient is a well-defined measurement of boundary structures, which have been proved as features of interest in many applications. The shape view descriptor is designed to evaluate the overall orientation of features of interest. For estimating local details, we employ the bilateral filter to construct the shape volume. The bilateral filter is very effective in smoothing local details and preserving strong boundary structures at the same time. Therefore, large-scale global structures are in the shape volume, while small-scale local details still remain in the original volume. The detail view descriptor measures the amount of visible details on boundary structures in terms of variances in the local structure between the shape volume and the original volume. These two view descriptors can be integrated into a viewpoint selection framework, and this framework can emphasize global structures or local details with flexibility tailored to the user´s specific situations. We performed experiments on various types of volume datasets. These experiments verify the effectiveness of our proposed view descriptors, and the proposed viewpoint selection framework actually locates the optimal viewpoints that show the maximum amount of the structural information.