Isovist

For the radiocontrast agent, see Iotrolan.

The pale blue area is the point isovist that can be seen from the centre of the circle

A single isovist is the volume of space visible from a given point in space, together with a specification of the location of that point. Isovists are naturally three-dimensional, but they may also be studied in two dimensions: either in horizontal section ("plan") or in other vertical sections through the three-dimensional isovist. Every point in physical space has an isovist associated with it.

The boundary-shape of an isovist may or may not vary with location in, say, a room. If the room is convex (for example, a rectangle or circle), then the boundary-shape of every isovist in that room is the same; and so is its volume (or area, if we are thinking in plan). But the location of the viewpoint relative to the boundary would or could be different. However, if the room were non-convex (for example, an L-shaped or partitioned room), then there would be many isovists whose volume (area) would be less than that of the whole room, and perhaps some that were the whole room; and many would have different, perhaps unique shapes: large and small, narrow and wide, centric and eccentric, whole and shredded.

One can also think of the isovist as the volume of space illuminated by a point source of light.

It is used in the field of architecture for analysis of buildings and urban areas, typically as one of a series of methods used in space syntax.

See also

• Art gallery theorem
• Viewshed
• Visibility (geometry)
• Visibility polygon

References

• A. Turner; Doxa, M.; O'Sullivan, D.; Penn, A. (2001). "From isovists to visibility graphs: a methodology for the analysis of architectural space" (PDF). Environment and Planning B. 28: 103–121. doi:10.1068/b2684.
• M. Benedikt (1979). "To take hold of space: isovists and isovist fields". Environment and Planning B. 6: 47–65. doi:10.1068/b060047.

External links

• Isovist_2-3: A free software for advanced, real-time, high definition isovist point, path and field analysis in architectural plan and section drawings.
• VisiLibity: A free open source C++ library for visibility computations in planar polygonal environments.
• Isovist program and Analyst: A free VB.NET program of 2D visibility algorithms.
• SULEIMAN W., JOLIVEAU T. & FAVIER E., 2011 - 3D Urban Visibility Analysis with Vector GIS Data. In GISRUK, University of Portsmouth, UK.
• SULEIMAN W., JOLIVEAU T. & FAVIER E., 2012 - A New Algorithm for 3D Isovist. In 15th International Symposium on Spatial Data Handling Geospatial dynamics, geosimulation and exploratory visualization, 22–24 August 2012 in Bonn, Germany.
• SULEIMAN W., JOLIVEAU T. & FAVIER E., 2012 - A New Algorithm for 3D Isovist. In 3U3D2012: USAGE, USABILITY, AND UTILITY OF 3D CITY MODELS, 29 to 31 October 2012, Nantes, France.
• SULEIMAN W., JOLIVEAU T. & FAVIER E., 2012 - Une nouvelle méthode de calcul d’isovist en 2 et 3 dimensions. Sageo 2012, 6-9 novembre 2012, Université de Liège, Belgique.