{#sec:designgoals}
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The visualization techniques proposed in this paper have been developed with certain design goals in mind. While these goals are formulated with the application of vessel visualization in mind, we believe that many of them are also relevant for medical visualization in general, and beyond.

**Morphological features.** When inspecting complex 3D structures such as vessel trees, it is of uttermost importance that depth and shape are communicated effectively. Especially for vessels, these two parameters are intervened. Adequately communicating the depth of various vessel branches also facilitates the communication of the overall shape of the vascular tree. Besides these global shape parameters, also the details on the surface of a vessel need to be communicated, as these might give hints to initial aneurysms or other abnormalities. Consequently, depth and shape of a vessel need to be communicated efficiently to be able to decipher the structure of a vessel.

**Functional parameters.** Apart from these morphological features, often functional features are relevant in vessel visualization. Such parameters include wall shear stress and pressure in hemodynamics, elasticity, occurrence of plaque, or vascular constrictions, just to name a few. As in many subareas of medical visualization, where multiparametric or multimodal data needs to 