In this paper we suggest that the 3D isovists centered on a display have an impact on the ‘noticeability’ of the information presented on it. We compared the use of 2D and 3D isovists as methods of assessing display ‘noticeability’ applied to an environment in which a network of public digital displays has been installed, namely a university campus. We tested 2D and 3D isovists against observations, and experimental methods are employed in order to compare the observed recognition of display-content against the spatial attributes of the display. This paper introduces new software, ‘Nebula‘, that analyses real world scan isovists’ point clouds using a number of different 3D, volumetric approximations. For the university campus we studied, we found that 3D isovist volume improves the correlation between the recall of display content (when normalized for the number of viewers), over 2D isovist area or other measures. On the basis of this research we recommend the use of both 3D and 2D scanned isovists as a new analytical tool for the study of architectural environments.