Gypaets/findTheHole​s

Mesh reconstruction and hole finding in a point cloud

[triangulation, holes] = findTheHoles(XY,S,M,T)
% Definition
findTheHoles is a 2D mesh reconstruction tool which automatically
identifies holes in a points cloud.
% Usage
Input:
XY= Nx2 matrix with point coordinates.
Optional arguments:
S = Critical area ratio (real and positive number). Knots with a value
higher than the ratio of maximum to minimum neighbouring polygon
area are identified as hole-border points. Default value is 3.
M = Flag for manual editing. Default value is 0.
0: No manual editing.
1: Manual editing of hole-border points. After the first calculation
a figure with the point cloud is opened. Automatically recognized
points are marked with an 'x'. The user can add/remove
not/wrongly recognized border points selecting them with the
brush and clicking the appropiate button.
T = Triangulation (Nx3 matrix with polygon vertices). If not given the
delaunay triangulation of X,Y is used.
Output:
triangulation
.Points: nx2 matrix with points' coordinates.
.ConnectivityList: nx3 matrix with the triangulation polygons.
holes: Cell array. Each cell element is an nx1 matrix with ordered
hole border point indices.

% Method
To identify the holes a triangulation of the points cloud is needed. If
none is given, the delaunay triangulation is used. Points where the
ratio between maximum and minimum neighbouring polygon area exceeds a
critical value are identified as hole-border points. Polygons for which
all vertices are identified as hole-border points are deleted.
The adjacency matrix of the resulting mesh is clustered to get the
holes.
% Issues
The clustering algorithm isn't fully developed yet and has issues with
interconnected holes among others.

% Examples
See file examples_findTheHoles.m