adding inner and outer offsets

Author: romanarust

docs/examples/straight_skeleton_offset.py

@@ -0,0 +1,36 @@
+from compas.datastructures import Graph
+from compas.geometry import Polygon
+from compas_cgal.straight_skeleton_2 import create_offset_polygons_2
+from compas_viewer import Viewer
+
+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)
+offset = 1.5
+
+offset_polygons_inner = create_offset_polygons_2(points, offset)
+offset_polygons_outer = create_offset_polygons_2(points, -offset)
+
+# ==============================================================================
+# Viz
+# ==============================================================================
+
+viewer = Viewer(width=1600, height=900)
+viewer.scene.add(polygon)
+
+for opolygon in offset_polygons_inner:
+    viewer.scene.add(opolygon, linecolor=(1.0, 0.0, 0.0))
+for opolygon in offset_polygons_outer:
+    viewer.scene.add(opolygon, linecolor=(0.0, 0.0, 1.0))
+
+viewer.show()

src/compas_cgal/straight_skeleton_2.py

@@ -1,5 +1,6 @@
 import numpy as np
 from compas.geometry import normal_polygon
+from compas.geometry import Polygon
 from compas.tolerance import TOL
 
 from compas_cgal._cgal import straight_skeleton_2
@@ -66,3 +67,17 @@ def create_interior_straight_skeleton_with_holes(points, holes) -> PolylinesNump
         hole = np.asarray(points, dtype=np.float64)
         H.append(hole)
     return straight_skeleton_2.create_interior_straight_skeleton_with_holes(V, H)
+
+
+def create_offset_polygons_2(points, offset) -> PolylinesNumpy:
+    points = list(points)
+    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)
+    offset = float(offset)
+    if offset < 0: # outside
+        offset_polygons = straight_skeleton_2.create_offset_polygons_2_outer(V, abs(offset))[1:] # first one is box
+    else: # inside
+        offset_polygons = straight_skeleton_2.create_offset_polygons_2_inner(V, offset)
+    return [Polygon(points.tolist()) for points in offset_polygons]
+

src/straight_skeleton_2.cpp

@@ -3,6 +3,7 @@
 #include <CGAL/Polygon_2.h>
 #include <CGAL/create_straight_skeleton_2.h>
 #include <CGAL/create_straight_skeleton_from_polygon_with_holes_2.h>
+#include <CGAL/create_offset_polygons_2.h>
 
 typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
 typedef K::Point_2 Point;
@@ -12,6 +13,8 @@ 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;
+typedef boost::shared_ptr<Polygon_2> PolygonPtr;
+typedef std::vector<PolygonPtr> PolygonPtrVector;
 
 compas::Edges pmp_create_interior_straight_skeleton(
     Eigen::Ref<const compas::RowMatrixXd> &V)
@@ -86,6 +89,52 @@ compas::Edges pmp_create_interior_straight_skeleton_with_holes(
 
 }
 
+std::vector<compas::RowMatrixXd> pmp_create_offset_polygons_2_inner(Eigen::Ref<const compas::RowMatrixXd> &V, double &offset){
+    Polygon_2 poly;
+    for (int i = 0; i < V.rows(); i++){
+        poly.push_back(Point(V(i, 0), V(i, 1)));
+    }
+    PolygonPtrVector offset_polygons = CGAL::create_interior_skeleton_and_offset_polygons_2(offset, poly);
+
+    std::vector<compas::RowMatrixXd> result;
+    for(auto pi = offset_polygons.begin(); pi != offset_polygons.end(); ++pi){
+        std::size_t n = (*pi)->size();
+        compas::RowMatrixXd points(n, 3);
+        int j = 0;
+        for (auto vi = (*pi)->vertices_begin(); vi != (*pi)->vertices_end(); ++vi){
+            points(j, 0) = (double)(*vi).x();
+            points(j, 1) = (double)(*vi).y();
+            points(j, 2) = 0;
+            j++;
+        }
+        result.push_back(points);
+    }
+    return result;
+}
+
+std::vector<compas::RowMatrixXd> pmp_create_offset_polygons_2_outer(Eigen::Ref<const compas::RowMatrixXd> &V, double &offset){
+    Polygon_2 poly;
+    for (int i = 0; i < V.rows(); i++){
+        poly.push_back(Point(V(i, 0), V(i, 1)));
+    }
+    PolygonPtrVector offset_polygons = CGAL::create_exterior_skeleton_and_offset_polygons_2(offset, poly);
+
+    std::vector<compas::RowMatrixXd> result;
+    for(auto pi = offset_polygons.begin(); pi != offset_polygons.end(); ++pi){
+        std::size_t n = (*pi)->size();
+        compas::RowMatrixXd points(n, 3);
+        int j = 0;
+        for (auto vi = (*pi)->vertices_begin(); vi != (*pi)->vertices_end(); ++vi){
+            points(j, 0) = (double)(*vi).x();
+            points(j, 1) = (double)(*vi).y();
+            points(j, 2) = 0;
+            j++;
+        }
+        result.push_back(points);
+    }
+    return result;
+}
+
 // ===========================================================================
 // PyBind11
 // ===========================================================================
@@ -104,4 +153,16 @@ void init_straight_skeleton_2(pybind11::module &m)
         &pmp_create_interior_straight_skeleton_with_holes,
         pybind11::arg("V").noconvert(),
         pybind11::arg("holes").noconvert());
+
+    submodule.def(
+        "create_offset_polygons_2_inner",
+        &pmp_create_offset_polygons_2_inner,
+        pybind11::arg("V").noconvert(),
+        pybind11::arg("offset").noconvert());
+
+    submodule.def(
+        "create_offset_polygons_2_outer",
+        &pmp_create_offset_polygons_2_outer,
+        pybind11::arg("V").noconvert(),
+        pybind11::arg("offset").noconvert());
 };

src/straight_skeleton_2.h

@@ -7,9 +7,16 @@
 compas::Edges pmp_create_interior_straight_skeleton(
     Eigen::Ref<const compas::RowMatrixXd> &V);
 
-
 compas::Edges pmp_create_interior_straight_skeleton_with_holes(
     Eigen::Ref<const compas::RowMatrixXd> &V,
     std::vector<Eigen::Ref<const compas::RowMatrixXd>> &holes);
 
+std::vector<compas::RowMatrixXd> pmp_create_offset_polygons_2_inner(
+    Eigen::Ref<const compas::RowMatrixXd> &V,
+    double &offset);
+
+std::vector<compas::RowMatrixXd> pmp_create_offset_polygons_2_outer(
+    Eigen::Ref<const compas::RowMatrixXd> &V,
+    double &offset);
+
 #endif /* COMPAS_STRAIGHT_SKELETON_2_H */

tests/test_straight_skeleton_2.py

@@ -2,7 +2,7 @@
 
 from compas_cgal.straight_skeleton_2 import create_interior_straight_skeleton
 from compas_cgal.straight_skeleton_2 import create_interior_straight_skeleton_with_holes
-
+from compas_cgal.straight_skeleton_2 import create_offset_polygons_2
 
 def test_straight_polygon():
     points = [
@@ -73,3 +73,21 @@ def test_straight_polygon_2_compare():
         # the line direction sometimes changes ...
         assert TOL.is_allclose(sa, se) or TOL.is_allclose(sa, ee)
         assert TOL.is_allclose(ea, ee) or TOL.is_allclose(ea, se)
+
+
+def test_offset():
+    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),
+    ]
+    offset = 0.5
+    polygons = create_offset_polygons_2(points, offset)
+    assert len(polygons) == 1, len(polygons)
+    polygons = create_offset_polygons_2(points, -offset)
+    assert len(polygons) == 1, len(polygons)