  Depth perception in volumetric visualization plays a crucial role in the
understanding and interpretation of volumetric data. Numerous visualization
techniques, many of which rely on physically based optical effects, promise to
improve depth perception but often do so without considering camera movement or
the content of the volume. As a result, the findings from previous studies may
not be directly applicable to crowded volumes, where a large number of
contained structures disrupts spatial perception. Crowded volumes therefore
require special analysis and visualization tools with sparsification
capabilities. Interactivity is an integral part of visualizing and exploring
crowded spaces, but has received little attention in previous studies. To
address this gap, we conducted a study to assess the impact of different
rendering techniques on depth perception in crowded volumes, with a particular
focus on the effects of camera movement. The results show that depth perception
considering camera motion depends much more on the content of the volume than
on the chosen visualization technique. Furthermore, we found that traditional
rendering techniques, which have often performed poorly in previous studies,
showed comparable performance to physically based methods in our study.
