How to add hatches in AutoCAD so that they overlap each other?

Question

I am using the Python language and the win32com.client library to add hatches to a drawing.

Here is the code that implements the creation of hatchings:

import win32com.client
import pythoncom

acad = win32com.client.Dispatch("AutoCAD.Application")
acadModel = acad.ActiveDocument.ModelSpace 

def APoint(x, y, z = 0):
    return win32com.client.VARIANT(pythoncom.VT_ARRAY | pythoncom.VT_R8, (x, y, z))

def ADouble(xyz):
    return win32com.client.VARIANT(pythoncom.VT_ARRAY | pythoncom.VT_R8, (xyz))

def variants(object):
    return win32com.client.VARIANT(pythoncom.VT_ARRAY | pythoncom.VT_DISPATCH, (object))

out_loop = [acadModel.AddPolyline(ADouble([0,0,0,1000,0,0,1000,1000,0,0,1000,0,0,0,0]))]

hatch = acadModel.AddHatch(0, "HEX", True)
hatch.PatternScale = 20
hatch.AppendOuterLoop(variants(out_loop))
hatch.Evaluate()

hatch = acadModel.AddHatch(0, "ANSI31", True)
hatch.PatternScale = 10
hatch.AppendOuterLoop(variants(out_loop))
hatch.Evaluate()

The task is to find a solution to overlapping hatches on each other, which can be implemented using python. The desired result is shown on the right side of the picture.

I can do this task manually in autocad using the Explode command to the first hatch and then add a second hatch. But I need to implement this using Python.

I was also advised a method where WipeOut and SuperHatch are used, but I still haven't figured out how to implement this in code. (https://stackoverflow.com/a/77905739/23389658)

Maybe it need to modify the autocad scripts, with lisp or Autolisp. I don't know.

Answer 1

Unfortunately I haven't found a solution using ActiveX (COM), mainly because Hatch doesn't have an explode method. I suggest using PyRx - Python wrapper over Object ARX.

In a nutshell:

• create a HEX hatch,
• explode into single lines,
• connect the lines into hexagons,
• add target hatching by cutting out hexagons.

import traceback
from itertools import pairwise
from typing import Iterable, Tuple

import numpy as np
import shapely
from pyrx_imp import Db, Ge
from shapely.ops import linemerge


def PyRxCmd_doit():
    try:
        
        # HEX hatch
        hex_hatch = Db.Hatch()
        hex_hatch.setDatabaseDefaults()
        hex_hatch.setPattern(Db.HatchPatternType.kPreDefined, "HEX")

        outer_edges = (
            ((0.0, 0.0), (100.0, 0.0)),
            ((100.0, 0.0), (100.0, 100.0)),
            ((100.0, 100.0), (0.0, 100.0)),
            ((0.0, 100.0), (0.0, 0.0)),
        )

        outer_segments = [
            Ge.LineSeg2d(Ge.Point2d(p1), Ge.Point2d(p2)) for p1, p2 in outer_edges
        ]

        hex_hatch.appendLoopEdges(
            Db.HatchLoopType.kExternal,
            outer_segments,
            [Db.HatchEdgeType.kLine for _ in outer_segments],
        )
        hex_hatch.evaluateHatch()

        # explode hatch and get single lines
        hex_lines_ents = hex_hatch.explode()
        hex_lines = [Db.Line.cast(ent) for ent in hex_lines_ents]

        # connect individual lines in a "polyline" so that you can 
        # create loops for cutting the target hatch; round the coordinates 
        # so that the lines connect properly
        hex_lines_points = [
            (
                np.round(i.startPoint().toTuple()[:2], 6),
                np.round(i.endPoint().toTuple()[:2], 6),
            )
            for i in hex_lines
        ]

        plines = get_plines(hex_lines_points)  # get_plines below

        # Target hatch
        hatch = Db.Hatch()
        hatch.setPattern(Db.HatchPatternType.kPreDefined, "ANSI31")

        hatch.appendLoopEdges(
            Db.HatchLoopType.kExternal,
            outer_segments,
            [Db.HatchEdgeType.kLine for _ in outer_edges],
        )

        for pline in plines:  # hex plines
            
            # create a list of segments that make up the polylines of one hexagon
            line_segments = [
                Ge.LineSeg2d(Ge.Point2d(p1), Ge.Point2d(p2))
                for p1, p2 in pairwise(pline)
            ]
            hatch.appendLoopEdges(
                Db.HatchLoopType.kDefault,
                line_segments,
                [Db.HatchEdgeType.kLine for _ in line_segments],
            )

        hatch.evaluateHatch()

        db = Db.HostApplicationServices().workingDatabase()
        model = Db.BlockTableRecord(db.modelSpaceId(), Db.OpenMode.kForWrite)
        model.appendAcDbEntity(hatch)  # add hatch to the model
        model.appendAcDbEntities(hex_lines)  # add hexagon lines if needed too
        model.close()
        
    except Exception:
        traceback.print_exc()


Point_T = Tuple[float, float]

def get_plines(
    line_points: Iterable[Tuple[Point_T, Point_T]]
) -> Iterable[Iterable[Point_T]]:
    line_strings = linemerge(line_points)
    if isinstance(line_strings, shapely.LineString):
        line_strings = (line_strings,)
    elif isinstance(line_strings, shapely.MultiLineString):
        pass
    else:
        raise TypeError
    for line_string in line_strings.geoms:
        ch = line_string.convex_hull
        if isinstance(ch, shapely.Polygon):
            yield ch.exterior.coords

Problems to solve

The algorithm requires refinement at the hatch outer edge; the beginning and end of a polyline that is part of a hexagon are connected straight ahead instead of along the outer hatch outline; I suggest playing with shapely - create a HEX hatch whose outline is larger than the target hatch, and cut the polylines (get_plines() above) of this hatch from the polygon (shapely.Polygon) of the target hatch.

---

PyRx

• Install the latest release,
• Start AutoCAD and allow the PyRx.arx add-in to load,
• From the command line, run the PYLOAD command and select the python module with your code,
• Invoke the DOIT command (PyRxCmd_doit).

PyRx allows user interaction, for the user to specify the external hatch outline, use the Ed module (from pyrx_imp import Ed)

You can also use ActiveX (Autocad Object Model) with PyRx, check it out:

from pyrx_impx import Ax

doc = Ax.getDbx()  # same as acad.ActiveDocument