VoxR (version 1.0.0)

substract_point_clouds: Point clouds substraction: identification of changes between two measuring times.

Description

Identify the point that are unique to one of two point clouds to detect the changes that occured between two measuring times (e.g. growth, branches losses, branch motion). Two methods are available (see details).

Usage

substract_point_clouds(t0, t1, method, dist, message)

Arguments

t0

a data.frame or data.table containing the x, y, z, ... coordinates of a point cloud or voxel cloud acquired at time 0.

t1

a data.frame or data.table containing the x, y, z, ... coordinates of a point cloud or voxel cloud acquired at time 1.

method

character. The method to use to identify the difference between t0 and t1. Can be either "hull" or "distance", see details.

dist

numeric. The threshold distance to consider a point is unique to t1 if method = "distance".

message

logical. If FALSE, messages are disabled. Default = TRUE.

Value

a data.frame or data.table containing the x, y, z, ... coordinates of points that are unique to t1.

Details

If method = "hull", the convex hull that wraps t0 is constructed and the difference between t1 and t0 are the points outside the convex hull. If method = "distance", the points in t1 that are distant (i.e. further than dist) from the points in t0 are returned.

Examples

# NOT RUN {
#- import datasets
t0=data.table::fread(system.file("extdata", "Tree_t0.asc", package="VoxR"))
t1=data.table::fread(system.file("extdata", "Tree_t1.asc", package="VoxR"))

#- keep only the tree crown
t0 = t0[z>=0,]
t1 = t1[z>=0,]

####- substract t0 to t1 with the hull method
diff = VoxR::substract_point_clouds(t0 = t0,t1 = t1, method = "hull")
#- plot the result (t0 in black, the difference between t1 and t0 in red)
rgl::open3d()
rgl::plot3d(t0,add=TRUE)
rgl::plot3d(diff,col="red",add=TRUE)

####- substract t0 to t1 with the distance based method
diff = substract_point_clouds(t0 = t0,t1 = t1, method = "distance",dist = 0.1)
#- plot the result (t0 in black, the difference between t1 and t0 in red)
rgl::open3d()
rgl::plot3d(t0,add=TRUE)
rgl::plot3d(diff,col="red",add=TRUE)
# }