reserve the color channel on the vessels for parameter mappings.

**Iso-Lines.** Inspired by topographic maps, we also incorporate iso-lines which are displayed on the VSS to aid the perception of shape. The elevation and curvature of the surface are indicated by the form and density of the level sets. More iso-lines help to convey local changes, but too many can lead to clutter at large depth differences, especially between close structures. In the case of neighboring structures which are adjacent to the same void space, iso-lines help to distinguish points with small depth differences more easily. A comparison of different amounts of iso-lines on our VSS is presented in Figure \[fig:isolines\_comparison\].

Functional Parameter Mapping
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After all depth cues have been shifted away from the vascular surface model, functional parameters can be mapped on a vessel’s surface without resulting in interference as shown in Figure \[fig:parameter\_mapping\]. While communicating information such as wall shear stress or pressure, the applied color coding of these properties has to be considered. For the best contrast to the VSS, complementary or unused colors should be used instead of similar ones, which might result in confusion. Therefore, the 