Package {ahull3D}

Title:	Fast 3D Alpha Hull with Label Propagation
Version:	1.0.0
Date:	2026-06-26
Description:	Fast 3D alpha shape (alpha hull) computation with label propagation from input points to hull vertices and faces. Uses 'CGAL' for robust geometric computations. Optimized for Light Detection and Ranging ('LiDAR') processing and tree segmentation workflows. The implementation follows the alpha shape algorithm described in Edelsbrunner et al. (1983) <doi:10.1007/BF02579193>.
License:	MIT + file LICENSE
URL:	https://github.com/DijoG/ahull3D
BugReports:	https://github.com/DijoG/ahull3D/issues
Depends:	R (≥ 3.5.0)
Imports:	Rcpp (≥ 1.0.8), rgl (≥ 0.100.0), Rvcg (≥ 0.18.0)
Suggests:	RANN (≥ 2.6.0), testthat (≥ 3.0.0)
LinkingTo:	Rcpp, RcppEigen, RcppCGAL
SystemRequirements:	C++17
Encoding:	UTF-8
RoxygenNote:	7.3.1
NeedsCompilation:	yes
Packaged:	2026-07-07 11:56:47 UTC; Dijo
Author:	Gergo Dioszegi [aut, cre, cph]
Maintainer:	Gergo Dioszegi <dijogergo@gmail.com>
Repository:	CRAN
Date/Publication:	2026-07-16 12:50:30 UTC

Fast 3D Alpha Hull with Label Propagation

Description

Computes the alpha hull (alpha shape) of a 3D point cloud with optional label propagation for point classification.

Usage

ahull3D(points, alpha, input_truth = NULL, volume = FALSE)

Arguments

Value

A mesh object (from rgl::tmesh3d) with attributes: - input_truth: Propagated labels - face_truth: Labels for each face - alpha: Alpha value used - volume: Volume (if requested)

References

Edelsbrunner, H., Kirkpatrick, D., & Seidel, R. (1983). On the shape of a set of points in the plane. IEEE Transactions on Information Theory, 29(4), 551-559. <doi:10.1007/BF02579193>

Examples

# Small example for testing 
# Generate random points on a sphere
pts <- matrix(rnorm(100), ncol = 3)
pts <- pts / sqrt(rowSums(pts^2))

# Compute alpha hull
mesh <- ahull3D(pts, alpha = 0.5)

# Visualize
library(rgl)
shade3d(mesh, col = "lightblue")


# Larger example with visualization (may take longer)
pts <- matrix(rnorm(300), ncol = 3)
pts <- pts / sqrt(rowSums(pts^2))
mesh <- ahull3D(pts, alpha = 0.5)

# Visualize
library(rgl)
shade3d(mesh, col = "lightblue")

# Example with labels
pts <- matrix(rnorm(60), ncol = 3)
pts <- pts / sqrt(rowSums(pts^2))
labels <- rep(1:2, each = 10)
mesh_labeled <- ahull3D(pts, alpha = 0.5, input_truth = labels)
attr(mesh_labeled, "input_truth")

# Compute volume
mesh_vol <- ahull3D(pts, alpha = 0.8, volume = TRUE)
attr(mesh_vol, "volume")