R/algorithm-shp.R

In lidR: Airborne LiDAR Data Manipulation and Visualization for Forestry Applications

#' Algorithms for shape detection of the local point neighbourhood
#'
#' These functions are made to be used in \link{segment_shapes}. They implement algorithms for local
#' neighbourhood shape estimation.
#'
#' In the following, \eqn{a_1, a_2, a_3}{a1, a2, a3} denote the eigenvalues of the covariance matrix
#' of the neighbouring points in ascending order. \eqn{|Z_1|, |Z_2|, |Z_3|}{|Z1|, |Z2|, |Z3|} denote
#' the norm of the Z component of first, second and third axis of the decomposition.
#' \eqn{th_1, th_2, th_3}{th1, th2, th3}  denote a set of threshold values. Points are labelled
#' \code{TRUE} if they meet the following criteria. \code{FALSE} otherwise.\cr
#' \describe{
#' \item{shp_plane}{Detection of plans based on criteria defined by Limberger & Oliveira (2015) (see
#' references). A point is labelled TRUE if the neighborhood is approximately planar, that is:
#' \deqn{a_2 > (th_1 \times a_1) \& (th_2 \times a_2) > a_3}{a2 > (th1*a1) and (th2*a2) > a3}}
#' \item{shp_hplane}{The same as 'plane' but with an extra test on the orientation of the Z vector
#' of the principal components to test the horizontality of the surface.
#' \deqn{a_2 > (th_1 \times a_1) \& (th_2 \times a_2) > a_3 \& |Z_3| > th_3}{a2 > (th1*a1) and (th2*a2) > a3 and |Z3| > th3}
#' In theory  \eqn{|Z_3|}{|Z3|} should be exactly equal to 1. In practice 0.98 or 0.99 should be fine}
#' \item{shp_line}{Detection of lines inspired by the Limberger & Oliveira (2015) criterion. A point is
#' labelled TRUE if the neighbourhood is approximately linear, that is:
#' \deqn{th_1 \times a_2 < a_3 \& th_1 \times a_1 < a_3}{th1*a2 < a3 and th1*a1 < a3}}
#' \item{shp_hline}{Detection of horizontal lines inspired by the Limberger & Oliveira (2015) criterion.
#' A point is labelled TRUE if the neighbourhood is approximately linear and horizontal, that is:
#' \deqn{th_1 \times a_2 < a_3 \& th_1 \times a_1 < a_3 \& |Z_1| < th_2}{th1*a2 < a3 and th1*a1 < a3 and |Z1| < th2}
#' In theory \eqn{|Z_1|}{|Z1|} should be exactly equal to 0. In practice 0.02 or 0.01 should be fine}
#' \item{shp_vline}{Detection of vertical lines inspired by the Limberger & Oliveira (2015) criterion.
#' A point is labelled TRUE if the neighbourhood is approximately linear and vertical, that is:
#' \deqn{th_1 \times a_2 < a_3 \& th_1 \times a_1 < a_3 \& |Z_1| > th_2}{th1*a2 < a3 and th1*a1 < a3 and |Z1| > th2}
#' In theory \eqn{|Z_1|}{|Z1|} should be exactly equal to 1. In practice 0.98 or 0.99 should be fine}
#' }
#'
#' @param th1,th2,th3 numeric. Threshold values (see details)
#' @param k integer. Number of neighbours used to estimate the neighborhood.
#'
#' @references
#' Limberger, F. A., & Oliveira, M. M. (2015). Real-time detection of planar regions in unorganized
#' point clouds. Pattern Recognition, 48(6), 2043–2053. https://doi.org/10.1016/j.patcog.2014.12.020\cr\cr
#'
#' @examples
#' # Generating some data
#' n = 400
#' xplane = runif(n,0,6)
#' yplane = runif(n,0,6)
#' zplane = xplane + 0.8 * yplane + runif(n, 0, 0.1)
#' plane = data.frame(X = xplane, Y = yplane, Z = zplane)
#'
#' xhplane = runif(n,5,15)
#' yhplane = runif(n,0,10)
#' zhplane = 5 + runif(n, 0, 0.)
#' hplane = data.frame(X = xhplane, Y = yhplane, Z = zhplane)
#'
#' tline = 1:n
#' xline = 0.05*tline
#' yline = 0.01*tline
#' zline = 0.02*tline + runif(n, 0, 0.1)
#' line = data.frame(X = xline, Y = yline, Z = zline)
#'
#' thline = 1:n
#' xhline = 0.05*thline + runif(n, 0, 0.05)
#' yhline = 10 - 0.01*thline + runif(n, 0, 0.05)
#' zhline = 3 + runif(n, 0, 0.05)
#' hline = data.frame(X = xhline, Y = yhline, Z = zhline)
#'
#' tvline = 1:n
#' xvline = 5 + runif(n, 0, 0.05)
#' yvline = 5 + runif(n, 0, 0.05)
#' zvline = 0.02*tline
#' vline = data.frame(X = xvline, Y = yvline, Z = zvline)
#'
#' las <- rbind(plane, line, hplane, hline, vline)
#' las <- LAS(las)
#'
#' las <- segment_shapes(las, shp_plane(k = 20), "plane")
#' las <- segment_shapes(las, shp_hplane(k = 20), "hplane")
#' las <- segment_shapes(las, shp_line(k = 20), "line")
#' las <- segment_shapes(las, shp_hline(k = 20), "hline")
#' las <- segment_shapes(las, shp_vline(k = 20), "vline")
#'
#' #plot(las)
#' #plot(las, color = "plane")
#' #plot(las, color = "hplane")
#' #plot(las, color = "line")
#' #plot(las, color = "hline")
#' #plot(las, color = "vline")
#' @name shape_detection
#' @rdname shape_detection
NULL

#' @export
#' @rdname shape_detection
shp_plane = function(th1 = 25, th2 = 6, k = 8)
{
  assert_is_a_number(th1)
  assert_is_a_number(th2)
  assert_is_a_number(k)

  th1 <- lazyeval::uq(th1)
  th2 <- lazyeval::uq(th2)
  k   <- lazyeval::uq(k)

  f = function(las, filter)
  {
    assert_is_valid_context(LIDRCONTEXTSHP, "shp_plane")
    return(C_lasdetectshape(las, 1L , c(th1, th2), k, filter, getThread()))
  }

  f <- plugin_shape(f, TRUE)
  return(f)
}

#' @export
#' @rdname shape_detection
shp_hplane = function(th1 = 25, th2 = 6, th3 = 0.98, k = 8)
{
  assert_is_a_number(th1)
  assert_is_a_number(th2)
  assert_is_a_number(th3)
  assert_is_a_number(k)

  th1 <- lazyeval::uq(th1)
  th2 <- lazyeval::uq(th2)
  th3 <- lazyeval::uq(th3)
  k   <- lazyeval::uq(k)

  f = function(las, filter)
  {
    assert_is_valid_context(LIDRCONTEXTSHP, "shp_hplane")
    return(C_lasdetectshape(las, 2L , c(th1, th2, th3), k, filter, getThread()))
  }

  f <- plugin_shape(f, TRUE)
  return(f)
}

#' @export
#' @rdname shape_detection
shp_line = function(th1 = 10, k = 8)
{
  assert_is_a_number(th1)
  assert_is_a_number(k)

  th1 <- lazyeval::uq(th1)
  k   <- lazyeval::uq(k)

  f = function(las, filter)
  {
    assert_is_valid_context(LIDRCONTEXTSHP, "shp_line")
    return(C_lasdetectshape(las, 3L , th1, k, filter, getThread()))
  }

  f <- plugin_shape(f, TRUE)
  return(f)
}

#' @export
#' @rdname shape_detection
shp_hline = function(th1 = 10, th2 = 0.02, k = 8)
{
  assert_is_a_number(th1)
  assert_is_a_number(k)

  th1 <- lazyeval::uq(th1)
  th2 <- lazyeval::uq(th2)
  k   <- lazyeval::uq(k)

  f = function(las, filter)
  {
    assert_is_valid_context(LIDRCONTEXTSHP, "shp_line")
    return(C_lasdetectshape(las, 4L, c(th1, th2), k, filter, getThread()))
  }

  f <- plugin_shape(f, TRUE)
  return(f)
}

#' @export
#' @rdname shape_detection
shp_vline = function(th1 = 10, th2 = 0.98, k = 8)
{
  assert_is_a_number(th1)
  assert_is_a_number(k)

  th1 <- lazyeval::uq(th1)
  th2 <- lazyeval::uq(th2)
  k   <- lazyeval::uq(k)

  f = function(las, filter)
  {
    assert_is_valid_context(LIDRCONTEXTSHP, "shp_line")
    return(C_lasdetectshape(las, 5L , c(th1, th2), k, filter, getThread()))
  }

  f <- plugin_shape(f, TRUE)
  return(f)
}