different approach to communicate depth in vessel visualizations. They drew view-dependent circle glyphs on vessel end-points which encoded depth information. Moreover, they also proposed an algorithm to detect these points in vascular structures.

Whilst all these methods are focused on rendering extra information on top of the vessels, other techniques have centered their attention on communicating depth information through coloring the vessels. Ropinski et al. [@Ropinski2006] used a color scale based on the chromadepth technique composed of only two colors which encodes depth information. This color scale, named pseudo-chromadepth, performed better than other techniques in the user study carried out by the authors, as it resulted in more accurate and faster responses. Joshi et al. [@Joshi2008] presented a set of techniques to improve perception in visualizations of vascular structures represented by a volume data set. The authors used a similar color encoding as the one used in pseudo-chromadepth together with other illustrative visualization techniques such as tone shading or halos. In the same year, Chu et al. [@Chu2008] presented a technique which combined a similar color encoding to the one used in the chromadepth technique with hatching rendering and silhouettes. Kersten-Oertel et al. [@Kersten2014], in 2014, carried out a user 