Added straight skeleton 2

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+* Added `compas_cgal.straight_skeleton_2.create_interior_straight_skeleton`.
+
 ### Changed
 
 ### Removed

docs/api.rst

@@ -12,6 +12,7 @@ API Reference
     api/compas_cgal.reconstruction
     api/compas_cgal.slicer
     api/compas_cgal.skeletonization
+    api/compas_cgal.straight_skeleton_2
     api/compas_cgal.subdivision
     api/compas_cgal.triangulation
     api/compas_cgal.types

docs/api/compas_cgal.straight_skeleton_2.rst

@@ -0,0 +1,11 @@
+********************************************************************************
+compas_cgal.straight_skeleton_2
+********************************************************************************
+
+.. currentmodule:: compas_cgal.straight_skeleton_2
+
+.. autosummary::
+    :toctree: generated/
+    :nosignatures:
+
+    create_interior_straight_skeleton

docs/examples/straight_skeleton_2.py

@@ -0,0 +1,31 @@
+from compas.datastructures import Graph
+from compas.geometry import Polygon
+from compas_viewer import Viewer
+
+from compas_cgal.straight_skeleton_2 import create_interior_straight_skeleton
+
+points = [
+    (-1.91, 3.59, 0.0),
+    (-5.53, -5.22, 0.0),
+    (-0.39, -1.98, 0.0),
+    (2.98, -5.51, 0.0),
+    (4.83, -2.02, 0.0),
+    (9.70, -3.63, 0.0),
+    (12.23, 1.25, 0.0),
+    (3.42, 0.66, 0.0),
+    (2.92, 4.03, 0.0),
+    (-1.91, 3.59, 0.0),
+]
+polygon = Polygon(points)
+lines = create_interior_straight_skeleton(points)
+graph = Graph.from_lines(lines)
+
+# ==============================================================================
+# Viz
+# ==============================================================================
+
+viewer = Viewer(width=1600, height=900)
+viewer.renderer_config.show_grid = False
+viewer.scene.add(graph, edgecolor=(1.0, 0.0, 0.0))
+viewer.scene.add(polygon)
+viewer.show()

docs/examples/straight_skeleton_2.rst

@@ -0,0 +1,11 @@
+********************************************************************************
+2D Straight Skeleton
+********************************************************************************
+
+.. figure:: /_images/cgal_straight_skeleton_2.png
+    :figclass: figure
+    :class: figure-img img-fluid
+
+
+.. literalinclude:: straight_skeleton_2.py
+    :language: python

src/compas_cgal.cpp

@@ -12,6 +12,7 @@ void init_subdivision(pybind11::module &);
 void init_skeletonization(pybind11::module &);
 void init_reconstruction(pybind11::module &);
 void init_polygonal_surface_reconstruction(pybind11::module &);
+void init_straight_skeleton_2(pybind11::module &);
 
 // the first parameter here ("_cgal") will be the name of the "so" or "pyd" file that will be produced by PyBind11
 // which is the entry point from where all other modules will be accessible.
@@ -30,4 +31,5 @@ PYBIND11_MODULE(_cgal, m)
     init_skeletonization(m);
     init_reconstruction(m);
     init_polygonal_surface_reconstruction(m);
+    init_straight_skeleton_2(m);
 }

src/compas_cgal/__init__.py

@@ -22,6 +22,7 @@
     "compas_cgal.measure",
     "compas_cgal.slicer",
     "compas_cgal.triangulation",
+    "compas_cgal.straight_skeleton_2",
 ]
 
 __all__ = ["HOME", "DATA", "DOCS", "TEMP"]

src/compas_cgal/straight_skeleton_2.py

@@ -0,0 +1,33 @@
+import numpy as np
+from compas.geometry import normal_polygon
+from compas.tolerance import Tolerance
+
+from compas_cgal._cgal import straight_skeleton_2
+
+from .types import PolylinesNumpy
+
+
+def create_interior_straight_skeleton(points) -> PolylinesNumpy:
+    """Compute the skeleton of a polygon.
+
+    Parameters
+    ----------
+    points : list of point coordinates or :class:`compas.geometry.Polygon`
+        The points of the polygon.
+
+    Returns
+    -------
+    :attr:`compas_cgal.types.PolylinesNumpy`
+        The skeleton of the polygon.
+
+    Raises
+    ------
+    ValueError
+        If the normal of the polygon is not [0, 0, 1].
+    """
+    points = list(points)
+    tol = Tolerance()
+    if not tol.is_allclose(normal_polygon(points, True), [0, 0, 1]):
+        raise ValueError("Please pass a polygon with a normal vector of [0, 0, 1].")
+    V = np.asarray(points, dtype=np.float64)
+    return straight_skeleton_2.create_interior_straight_skeleton(V)

src/straight_skeleton_2.cpp

@@ -0,0 +1,56 @@
+
+#include "straight_skeleton_2.h"
+#include <CGAL/Polygon_2.h>
+#include <CGAL/create_straight_skeleton_2.h>
+
+typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
+typedef K::Point_2 Point;
+typedef CGAL::Polygon_2<K> Polygon_2;
+typedef CGAL::Straight_skeleton_2<K> Ss;
+typedef boost::shared_ptr<Ss> SsPtr;
+typedef CGAL::Straight_skeleton_2<K>::Halfedge_const_handle Halfedge_const_handle;
+typedef CGAL::Straight_skeleton_2<K>::Vertex_const_handle Vertex_const_handle;
+
+Edges pmp_create_interior_straight_skeleton(
+    Eigen::Ref<const compas::RowMatrixXd> &V)
+{
+    Polygon_2 poly;
+    for (int i = 0; i < V.rows(); i++)
+    {
+        poly.push_back(Point(V(i, 0), V(i, 1)));
+    }
+    assert(poly.is_counterclockwise_oriented());
+    SsPtr iss = CGAL::create_interior_straight_skeleton_2(poly.vertices_begin(), poly.vertices_end());
+    Edges edgelist;
+    for(auto hit = iss->halfedges_begin(); hit != iss->halfedges_end(); ++hit){
+        const Halfedge_const_handle h = hit;
+        if(!h->is_bisector()){
+            continue;
+        }
+        const Vertex_const_handle& v1 = h->vertex();
+        const Vertex_const_handle& v2 = h->opposite()->vertex();
+        if(&*v1 < &*v2){
+            std::vector<double> s_vec = {v1->point().x(), v1->point().y(), 0};
+            std::vector<double> t_vec = {v2->point().x(), v2->point().y(), 0};
+            Edge edge = std::make_tuple(s_vec, t_vec);
+            edgelist.push_back(edge);
+        }
+
+    }
+    return edgelist;
+};
+
+
+// ===========================================================================
+// PyBind11
+// ===========================================================================
+
+void init_straight_skeleton_2(pybind11::module &m)
+{
+    pybind11::module submodule = m.def_submodule("straight_skeleton_2");
+
+    submodule.def(
+        "create_interior_straight_skeleton",
+        &pmp_create_interior_straight_skeleton,
+        pybind11::arg("V").noconvert());
+};

src/straight_skeleton_2.h

@@ -0,0 +1,12 @@
+#ifndef COMPAS_STRAIGHT_SKELETON_2_H
+#define COMPAS_STRAIGHT_SKELETON_2_H
+
+#include <compas.h>
+
+typedef std::tuple<std::vector<double>, std::vector<double>> Edge;
+typedef std::list<Edge> Edges;
+
+Edges pmp_create_interior_straight_skeleton(
+    Eigen::Ref<const compas::RowMatrixXd> &V);
+
+#endif /* COMPAS_STRAIGHT_SKELETON_2_H */

tests/test_straight_skeleton_2.py

@@ -0,0 +1,16 @@
+from compas_cgal.straight_skeleton_2 import create_interior_straight_skeleton
+
+
+def test_straight_polygon():
+    points = [
+        (-1, -1, 0),
+        (0, -12, 0),
+        (1, -1, 0),
+        (12, 0, 0),
+        (1, 1, 0),
+        (0, 12, 0),
+        (-1, 1, 0),
+        (-12, 0, 0),
+    ]
+    lines = create_interior_straight_skeleton(points)
+    assert len(lines) == 8