CGAL on Rhino8 ScriptEditor

Scripting
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21

Here is a snippet, using the compas_CGAL interior_straight_skeleton() function, and showing how to write compas geometry into the rhino drawing.

Useful in drawing plans of hipped roofs.

# Draw a 'Straight Skeleton' into an anti-clockwise closed non-intersecting planar polyline
# A straight skeleton describes the plan of ridges and valleys in a hipped roof.

#! python 3
# r: compas, compas_cgal

import rhinoscriptsyntax as rs
import scriptcontext as sc

from compas.geometry import Point, Polygon, Line
from compas_cgal.straight_skeleton_2 import interior_straight_skeleton
import compas_rhino.objects
import compas_rhino.conversions

obj = rs.GetObject("Select a polyline", rs.filter.curve)
poly_points = []

if obj and rs.IsPolyline(obj):
    pts = rs.PolylineVertices(obj)
    for pt in pts:
        poly_points.append(Point(pt.X, pt.Y, pt.Z))

polyg = Polygon(poly_points)
graph = interior_straight_skeleton(polyg)

for edge in graph.edges():
    edge_line = graph.edge_line(edge)
    rh_ln = compas_rhino.conversions.line_to_rhino(edge_line)
    sc.doc.Objects.AddLine(rh_ln)
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Straight skeleton extrusion has been added to compas_cgal. Incase you need to model or draw roofscapes:

example_straight_skeleton_2_extrude
example_straight_skeleton_2_extrude1530×999 8.86 KB

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Here is a rough sketch for generating ‘hipped roof’ forms.
Thanks Petras!

# Draw a hipped roof form - aka an extruded straight skeleton.
# Outputs a mesh and edge lines
# Uses compas_cgal python bindings for CGAL geometry library.  
# Thanks Petras Vestartas & ETH Zurich.

#! python 3
# r: compas, compas_cgal

import rhinoscriptsyntax as rs
import scriptcontext as sc
from compas.geometry import Point, Polygon, Line
from compas_cgal.straight_skeleton_2 import interior_straight_skeleton
from compas_cgal.straight_skeleton_2 import extrude
import compas_rhino.objects
import compas_rhino.conversions

def extrude_straight_skeleton():
    TOLERANCE = 0.06
    obj = rs.GetObject("Select a boundary polyline: ", rs.filter.curve)
    poly_points = []
    if obj and rs.IsPolyline(obj):
        pts = rs.PolylineVertices(obj)
        for pt in pts:
            poly_points.append(Point(pt.X, pt.Y, pt.Z))
    polyg = Polygon(poly_points)

    holes_objs = rs.GetObjects("Select any non-overlapping Holes: ", rs.filter.curve)
    holes = []
    if holes_objs:
        for hl in holes_objs:
            if rs.IsPolyline(hl):
                poly_points = []
                pts = rs.PolylineVertices(hl)
                for pt in pts:
                    poly_points.append(Point(pt.X, pt.Y, pt.Z))
                poly_hole = Polygon(poly_points)
                holes.append(poly_hole)
    if len(holes) == 0:
        holes = None
    mesh, lines = extrude(polyg, holes=holes, angles=22.5)
    for line in lines:
        rh_ln = compas_rhino.conversions.line_to_rhino(line)
        sc.doc.Objects.AddLine(rh_ln)
    rh_msh = compas_rhino.conversions.mesh_to_rhino(mesh)
    # unites the mesh from cgal into flat planes
    rh_msh.Weld(TOLERANCE)
    rh_msh.MergeAllCoplanarFaces(TOLERANCE)
    sc.doc.Objects.AddMesh(rh_msh) 

if __name__ == "__main__" :
    extrude_straight_skeleton()
24

@greenbox Can you post some example on more complex scene to stress test this method?