surfaceNormals: Normal vectors computation

Description

This function calculates the normal vectors of all the triangles which belong to the boundary of the $\alpha$-shape.

Usage

surfaceNormals(x, indexAlpha = 1, display = FALSE, col = 3, scale = 1,
  ...)

Value

If indexAlpha is a single value then the function returns an object of class "normals" with the following components:

normals: Three-column matrix with the euclidean coordinates of the normal vectors.
centers: Three-column matrix with the euclidean coordinates of the centers of the triangles that form the $\alpha$-shape.

Otherwise surfaceNormals returns a list of class "normals-List" (each object in the list as described above).

Arguments

x: An object of class "ashape3d" that represents the $\alpha$-shape of a given sample of points in the three-dimensional space, see ashape3d.
indexAlpha: A single value or vector with the indexes of as3d$alpha that should be used for the computation, see Details.
display: Logical, if TRUE, surfaceNormals open a new rgl device and display the related $\alpha$-shape and its normals vectors.
col: Color of the normal vectors.
scale: Scale parameter to control the length of the surface normals, only affect display.
...: Material properties. See material3d for details.

Details

The function surfaceNormals computes the normal vectors of all the triangles which belong to the boundary of the $\alpha$-shape for each value of $\alpha$ in x$alpha[indexAlpha]. The magnitude of each vector is equal to the area of its associated triangle.

If indexAlpha="all" or indexAlpha="ALL" then the function computes the normal vectors for all values of $\alpha$ in as3d$alpha.

Examples

Run this code


x <- rtorus(1000, 0.5, 1)
alpha <- 0.25
ashape3d.obj <- ashape3d(x, alpha = alpha)
surfaceNormals(ashape3d.obj, display = TRUE)