Straight Skeleton with Holes

This example demonstrates how to compute the straight skeleton of a polygon with holes using COMPAS CGAL.

Key Features:

• Computing straight skeleton for polygons with holes
• Handling multiple interior holes
• Color-coded visualization of different edge types
• Distinction between inner bisectors and regular edges

from compas.geometry import Polygon
from compas_viewer import Viewer

from compas_cgal.straight_skeleton_2 import interior_straight_skeleton_with_holes

# =============================================================================
# Outer boundary
# =============================================================================

points_boundary = [
    (-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),
]
boundary = Polygon(points_boundary)

# =============================================================================
# Inner holes
# =============================================================================

holes = [
    [(0.42, 0.88, 0.0), (1.1, -1.0, 0.0), (-1.97, -0.93, 0.0), (-1.25, 1.82, 0.0)],
    [(4.25, -0.64, 0.0), (2.9, -3.03, 0.0), (2.12, -2.16, 0.0), (2.89, -0.36, 0.0)],
    [(10.6, 0.29, 0.0), (9.48, -1.54, 0.0), (5.48, -1.26, 0.0), (5.98, -0.04, 0.0)],
]
holes = [Polygon(hole) for hole in holes]

# =============================================================================
# Skeleton
# =============================================================================

graph = interior_straight_skeleton_with_holes(boundary, holes)

# ==============================================================================
# Visualize
# ==============================================================================

viewer = Viewer()

for edge in graph.edges():
    line = graph.edge_line(edge)
    if graph.edge_attribute(edge, "inner_bisector"):
        viewer.scene.add(line, linecolor=(1.0, 0.0, 0.0), linewidth=2)
    elif graph.edge_attribute(edge, "bisector"):
        viewer.scene.add(line, linecolor=(0.0, 0.0, 1.0))
    else:
        viewer.scene.add(line, linecolor=(0.0, 0.0, 0.0))

viewer.show()