finding self-intersecting polylines and polylines with double vertices

Edgar_Miersch_1 · March 22

Hello, do any of you know a lisp tool for finding self-intersecting polylines and polylines with double vertices, similar to the "selfintersect.vlx" tool from this page?

https://www.cadforum.cz/en/self-intersecting-polylines-and-polylines-with-duplicate-vertice-tip10926

Or is there another way to accomplish this task in BricsCAD?
The problem is that BricsCAD apparently cannot process *.vlx files, and I have not yet found a corresponding *.lsp file online that does this job.

I myself work with BricsCAD version 23.1.08 (x64) and am more of a user than a programmer, which means I can't program LISP.

I need a tool like this to be able to create correct polylines for grading in BricsCAD-Civil. I often have to import these from "geometrically inaccurate sources" such as PDFs. Then I have to check the lines for errors, otherwise there will be problems when creating the grading. By the way, it would be good if there was a warning when creating the grading when you select a polyline with self-intersection, not just a cancellation or "not working" of the command.

Its_Alive · March 22

Too bad you’re not using V24, Python’s shapely has a tool for checking polygons
https://shapely.readthedocs.io/en/latest/manual.html#validation.make_valid

I’m not sure if it will catch all your issues, but in this case, it detects self-intersection and fixes it by creating MultiPolygon
Some sample code:


import traceback
from pyrx_imp import Rx
from pyrx_imp import Ge
from pyrx_imp import Gi
from pyrx_imp import Db
from pyrx_imp import Ap
from pyrx_imp import Ed
from pyrx_imp import Gs
from pyrx_imp import Cv

from shapely.validation import make_valid
from shapely.validation import explain_validity
from shapely.geometry.polygon import Polygon

def PyRxCmd_doit() -> None:
    try:
        db = Db.curDb()
        filter = [(Db.DxfCode.kDxfStart, "LWPOLYLINE")]
        ssres: tuple[Ed.PromptStatus,Ed.SelectionSet] = Ed.Editor.select(filter)
        if ssres[0] != Ed.PromptStatus.eOk:
                print("Oops {}: ".format(ssres[0])) 
                return

        for id in ssres[1].objectIds():
            pl = Db.Polyline(id)
            sp = Polygon(pl.toList())
            if not sp.is_valid:
                #why
                print(explain_validity(sp))
                #fix
                nsp = list(make_valid(sp).geoms)
                for spl in nsp:
                    npl = Db.Polyline(list(spl.exterior.coords))
                    npl.setColorIndex(3)
                    npl.setClosed(True)#?
                    db.addToCurrentspace(npl)

    except Exception as err:
        traceback.print_exception(err)

finding self-intersecting polylines and polylines with double vertices

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