05 · Attributes

Each part carries an attribute (a point at its centroid) that is transformed along with the part, so it ends up at the placed centroid. Any compas geometry can be carried this way.

from pathlib import Path

from compas.colors import Color
from compas.geometry import Point
from compas.geometry import Polyline
from compas.geometry import centroid_points
from compas_viewer import Viewer

from compas_nest import nest_geo
from compas_nest import nest_result
from compas_nest import nest_sheets
from compas_nest import opennest_collision

BLACK: Color = Color.from_hex("#000000")
BLUE: Color = Color.from_hex("#0072B2")
RED: Color = Color.from_hex("#C0392B")
OUTPUT: Path = Path(__file__).parent.parent / "data" / "output" / "05_attributes.json"


def centroid(polyline: Polyline) -> Point:
    return Point(*centroid_points(list(polyline.points)[:-1]))


# 1. parts, each carrying a point at its centroid as an attribute (moves with the part)
outlines = [
    Polyline([
        [0, 0, 0],
        [30, 0, 0],
        [30, 12, 0],
        [0, 12, 0],
        [0, 0, 0],
    ]),
    Polyline([
        [0, 0, 0],
        [20, 0, 0],
        [20, 20, 0],
        [0, 20, 0],
        [0, 0, 0],
    ]),
]

geo: nest_geo = nest_geo()
for outline in outlines:
    geo.add_part(outline, attributes=[centroid(outline)], copies=4)

sheets: nest_sheets = nest_sheets()
sheets.add_sheet(
    Polyline([
        [0, 0, 0],
        [120, 0, 0],
        [120, 120, 0],
        [0, 120, 0],
        [0, 0, 0],
    ]),
)

# 2. nest
result: nest_result = opennest_collision().solve(geo, sheets)

# 3. view: each placed element (outline + its centroid point) in its own scene group
viewer: Viewer = Viewer()
sheets_group = viewer.scene.add_group(name="sheets")
for i, sheet in enumerate(sheets.sheets):
    sheets_group.add(sheet["outline"], name="sheet_%d" % i, linecolor=BLACK, linewidth=2)

elements = viewer.scene.add_group(name="elements")
for k, group in enumerate(result.placed_polylines()):
    for j, part in enumerate(group["parts"]):
        element = viewer.scene.add_group(name="element_%d_%d" % (k, j), parent=elements)
        element.add(part["outline"], linecolor=BLUE, linewidth=2)
        for attribute in part["attributes"]:
            element.add(attribute, pointcolor=RED, pointsize=12)
viewer.show()

# 4. save to JSON (full result, incl. transformed attributes) and OBJ (outlines + holes)
result.to_json(OUTPUT)
result.to_obj(OUTPUT.with_suffix(".obj"))