of screen space area, most of the surrounding pixels closer to the image border approach the average value of the outermost silhouette. This forms a fairly dull surface which does not communicate a lot of depth and shape of the vascular model. Vessels which intersect the image border separate the VSS into multiple regions which describe their surrounding contours much more accurate. Generally speaking, for a meaningful overview and a significant global depth and shape impression, the vascular model should be kept as close as possible to the image boundary.

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Perceptual Enhancement
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Based on the VSS generation described in the previous subsection, we can now use the VSS as canvas for perceptual enhancements. Thus, VSS form a new foundation for a variety of depth enhancement techniques which have proven to be successful. Height field rendering would be the most similar field when it comes to the utilization of established depth and shape enhancement algorithms. In the following paragraphs, we would like to discuss a selection of depth enhancement techniques, which we found helpful in the context of vessel visualizations. We would like to point out, that this is not an exhaustive list of possibilities, but rather a 