Python for AutoCAD, Using shapely to find an oriented bounding box.

 

I see this asked frequently in the AutoCAD forums “How do I get the bounding box of an entity”, and the standard answer is usually, “Use vla-GetBoundingBox”, or get the entity extents. This is the correct answer, caveat, the bounding box is aligned with WCS, so if your object is rotated the result may not be what you need.

 One option is to transform the object to align with WCS. Or we can use a 3^rd party tool like Python’s shapely to help. 

 

here's an example:

import traceback

from pyrx import Ap, Ax, Db, Ed, Ge, Gi

from shapely import LineString

@Ap.Command()

def mybb() -> None:

    try:

        # create a selection set filter and select the polylines

        filter = [(Db.DxfCode.kDxfStart, "LWPOLYLINE")]

        ps, ss = Ed.Editor.selectPrompt("\nSelect parts: ", "\nRemove parts: ", filter)

        if ps != Ed.PromptStatus.eNormal:

            return

        # iterate the selection set

        for id in ss:

            # create a LineString from our polylines

            pline = Db.Polyline(id)

            ls = LineString(pline.toList())

            # get the oriented bbox

            coords = ls.oriented_envelope.exterior.coords

            # convert tuples to Ge.Point3d

            points = [Ge.Point3d(p) for p in coords]

            # #draw the results

            Ed.Core.grDraw(points[0], points[1], 1, 0)

            Ed.Core.grDraw(points[1], points[2], 1, 0)

            Ed.Core.grDraw(points[2], points[3], 1, 0)

            Ed.Core.grDraw(points[3], points[0], 1, 0)

    except Exception as err:

        traceback.print_exception(err)