| Title: | Geospatial Tools for Visibility Analysis |
| Version: | 0.1.0 |
| Description: | Provides tools for visibility analysis in geospatial data. It offers functionality to perform isovist calculations, using arbitrary geometries as both viewpoints and occluders. |
| License: | Apache License (≥ 2) |
| URL: | https://cityriverspaces.github.io/visor/, https://github.com/CityRiverSpaces/visor |
| BugReports: | https://github.com/CityRiverSpaces/visor/issues |
| Imports: | sf, sfheaders |
| Suggests: | knitr, rmarkdown, testthat (≥ 3.0.0) |
| Depends: | R (≥ 4.1.0) |
| Config/testthat/edition: | 3 |
| Encoding: | UTF-8 |
| RoxygenNote: | 7.3.2 |
| VignetteBuilder: | knitr |
| NeedsCompilation: | no |
| Packaged: | 2025-04-03 20:10:49 UTC; claudiuforgaci |
| Author: | Claudiu Forgaci 
[aut, cre, cph],
Francesco Nattino
[aut],
Netherlands eScience Center [fnd] |
| Maintainer: | Claudiu Forgaci <c.forgaci@tudelft.nl> |
| Repository: | CRAN |
| Date/Publication: | 2025-04-07 16:10:01 UTC |
Create a polygon representing an occluder
Description
Create a polygon representing an occluder
Usage
create_occluder(center_x, center_y, length, width)
Arguments
center_x |
Center x coordinate |
center_y |
Center y coordinate |
length |
Length of the occluder |
width |
Width of the occluder |
Value
object of class sfc_POLYGON
Examples
occluder <- create_occluder(0, 0, 10, 2)
Calculate isovist from one or multiple viewpoints
Description
Isovists are estimated by shooting a set of rays from each viewpoint, and by constructing the envelope of the (partially occluded) rays.
Usage
get_isovist(
viewpoints,
occluders = NULL,
ray_num = 40,
ray_length = 100,
remove_holes = TRUE
)
Arguments
viewpoints |
object of class sf_POINT or sfc_POINT |
occluders |
object of class sf, sfc or sfg |
ray_num |
number of rays per viewpoint. The number of rays per quadrant
needs to be a whole number, so |
ray_length |
length of rays |
remove_holes |
whether to remove holes from the overall isovist geometry |
Value
object of class sfc_POLYGON or sfc_MULTIPOLYGON
Examples
# Define viewpoints and occluder geometries
viewpoints <- sf::st_sfc(
sf::st_point(c(-1, 1)),
sf::st_point(c(0, 0)),
sf::st_point(c(1, -1))
)
occluder1 <- sf::st_polygon(list(sf::st_linestring(
cbind(c(-1, -1, -0.9, -0.9, -1),
c(-1, -0.9, -0.9, -1, -1))
)))
occluder2 <- sf::st_polygon(list(sf::st_linestring(
cbind(c(0.4, 0.4, 0.6, 0.6, 0.4),
c(0.5, 0.7, 0.7, 0.5, 0.5))
)))
occluders <- sf::st_sfc(occluder1, occluder2)
# Calculare isovist based on 40 rays (default)
get_isovist(viewpoints, occluders, ray_length = 1.5)
# Increase number of rays to get higher resolution
get_isovist(viewpoints, occluders, ray_num = 400, ray_length = 1.5)
Construct isovist from (partially occluded) rays
Description
Construct isovist from (partially occluded) rays
Usage
get_isovists(rays)
Arguments
rays |
object of class sf, including the "isovist_id" attribute |
Value
object of class sfc_POLYGON
Get rays from the viewpoints within a maximum isovist
Description
Get rays from the viewpoints within a maximum isovist
Usage
get_rays(viewpoints, ray_num = 40, ray_length = 100)
Arguments
viewpoints |
object of class sf_POINT or sfc_POINT |
ray_num |
number of rays. The number of rays per quadrant needs to be a
whole number, so |
ray_length |
length of rays |
Value
object of class sf_LINESTRING
Get viewpoints from an arbitrary geometry
Description
Generate a discrete set of points on the given geometry. If the geometry is a (MULTI)POLYGON, points are generated on its boundary.
Usage
get_viewpoints(x, density = 1/50)
Arguments
x |
object of class sf, sfc or sfg |
density |
number of points per distance unit |
Value
object of class sfc_POINT
Examples
line <- sf::st_linestring(cbind(c(-1, 1), c(0, 0)))
get_viewpoints(line, density = 5)
Merge the viewpoint isovists
Description
Merge the viewpoint isovists
Usage
merge_isovists(isovists, remove_holes = TRUE)
Arguments
isovists |
object of class sf, sfc or sfg |
remove_holes |
whether to remove holes from the overall isovist geometry |
Value
object of class sfc_POLYGON or sfc_MULTIPOLYGON
Determine the non-occluded segments of the rays
Description
Determine the non-occluded segments of the rays
Usage
occlude_rays(rays, occluders = NULL)
Arguments
rays |
object of class sf_LINESTRING |
occluders |
object of class sf, sfc or sfg |
Value
object of class sf_LINESTRING