sample_scene: Recenters and subsets a 3D scene for visibility estimates

In Blecigne/viewshed3d: Compute Viewshed in 3D Point Clouds of Ecosystems

Recenters and subsets a 3D scene for visibility estimates

Description

Recenters and if needed subsets a 3D scan image for use in the visibility function. Keeps the points that fall within a user defined distance from the animal location and recenters the scene so that the animal location in the output point has 0,0,0 coordinates. The animal location can be defined by providing xyz coordinates or can be manually selected within the scene. The scene shape can be spherical or circular (see details for more information).

Usage

sample_scene(data, scene_radius, scene_shape, center, downsample, messages)

Arguments

data	LAS class object containing the xyx coordinates of a 3D point cloud.
scene_radius	numerical. The radius of the final scene. Can refer to the radius of a sphere if scene_shape = "sph" or of a circle if scene_shape = "circ".
scene_shape	character string. Defines the shape of the scene: "sph" and "circ" are accepted (see details for more informations). Default = "circ".
center	(optional) vector of length 3 providing the xyz coordinates of the user defined animal location. If not provided, the user can manually select the animal location in the 3D point cloud. The average coordinates of the selected region will be set as the animal location (see details).
downsample	numeric. Enables the user to downsample the point cloud before visualizing it for scene center manual selection (if no center is provided). Defines the voxel resolution within which a single point of the input scene will be kept. downsample = 0 desable downsampling. Default is 0 if the scene contains less than 5e6 surveyed points or 0.1 if the scene contains more than 5e6 surveyed points.
messages	logical. Disables the messages and message box when manually selecting the scene center.

Details

Scene shape

if scene_shape = "circ" the distance to scene center is computed in the xy dimension of the original scene only, resulting in a circular scene. If scene_shape = "sph" the distance to the scene center is similar to arguments scene.radius in visibility function and cut_off in viewsheds.

Manual selection of scene center

if no center is provided, a 3D plot automatically opens. The user can navigate around the surveyed points (rotate = left click, pan = right click) and select points (in a rectangular region) with the middle click. Once the points are selected, a message box opens (if not disabled). If the user clicks "yes", the plot window closes and the average point coordinates are defined as the animal location. If the user clicks "no", he/she can revise the previous selection.

Value

A LAS class object containing the coordinates of the reshaped scene.

Examples

#- import the tree_line_plot dataset
file <- system.file("extdata", "tree_line_plot.laz", package="viewshed3d")
tls  <-  lidR::readLAS(file,select="xyz")

#- define the animal location
center <- c(0,-6,1)

#- reshape the TLS scene with scene_shape="circ" and the calculated center
reshaped <- viewshed3d::sample_scene(tls,scene_radius = 4,
                                     center=center,
                                     scene_shape = "circ")

lidR::plot(reshaped)

#- reshape the TLS scene with scene_shape="sph" and the calculated center
reshaped <- viewshed3d::sample_scene(tls,scene_radius = 4,
                                     center=center,
                                     scene_shape = "sph")

lidR::plot(reshaped)

if (interactive()){
#- manual selection of the center
reshaped <- viewshed3d::sample_scene(tls,scene_radius = 4,
                                     scene_shape = "circ")

lidR::plot(reshaped)
}

Blecigne/viewshed3d documentation built on Nov. 5, 2022, 9:08 p.m.