---
author:
- 'Julian Kreiser, *Student Member, IEEE*, Pedro Hermosilla, *Member, IEEE*, and Timo Ropinski, *Member, IEEE*'
bibliography:
- 'vis18voidspacesurfaces.bib'
title: |
    Void Space Surfaces\
    to Convey Depth in Vessel Visualizations
---

Introduction
============

Medical visualization is of key importance in many areas of medicine, such as surgery planning or education. Due to its relevance, researchers focused their attention on improving the perceptual capabilities of these visualizations [@Preim2016]. Realistic lighting simulations [@Magnus2018], illustrative techniques [@Bruckner2007] or different color schemes [@Borkin2011] are just some of the approaches that have been proposed in order to improve shape or depth perception.

Regarding visual perception, visualization of vascular structures is one of the most challenging areas of medical visualization. Vascular structures are composed of numerous branches, which are complex by nature, and can easily clutter the resulting visualization. This makes it difficult to infer the relative position of the individual branches even when realistic lighting effects are used. To further complicate the situation, often additional information associated with the surface of a vessel needs to be communicated. Such information contains for instance additionally acquired or derived parameters such as blood flow, pressure or wall shear stress, which are typically conveyed by stream lines, different 