Revcloud

[gswifort]

Are there any plans to add REVCLOUD support?

[mozman]

No.

[mozman]

FYI: REVCLOUD is not a special DXF element, just a strange LWPOLYLINE with lots of bulges

[mozman]

This script renders something similar, maybe I add the revcloud() function to the library:

# Copyright (c) 2024, Manfred Moitzi
# License: MIT License
from typing import Sequence
from pathlib import Path
import math
import ezdxf
from ezdxf.math import UVec, Vec2

CWD = Path("~/Desktop/Outbox").expanduser()
if not CWD.exists():
    CWD = Path(".")


def revcloud(
    points: UVec,
    segment_length: float,
    bulge: float = 0.5,
    start_width: float = 0.0,
    end_width: float = 0.0,
) -> list[Sequence[float]]:
    vertices = Vec2.list(points)
    if not vertices[0].isclose(vertices[-1]):
        vertices.append(vertices[0])
    lw_points: list[Sequence[float]] = []

    for s, e in zip(vertices, vertices[1:]):
        lw_points.append((s.x, s.y, start_width, end_width, bulge))
        diff = e - s
        length = diff.magnitude
        if length <= segment_length:
            continue

        count = math.ceil(length / segment_length)
        _segment_length = length / count
        offset = diff.normalize(_segment_length)
        for _ in range(count):
            s += offset
            lw_points.append((s.x, s.y, start_width, end_width, bulge))
    return lw_points


def main():
    doc = ezdxf.new()
    msp = doc.modelspace()
    lw_points = revcloud(
        [(0, 0), (1, 0), (1, 1), (0, 1)],
        segment_length=0.1,
        bulge=0.5,
        start_width=0,
        end_width=0.01,
    )
    msp.add_lwpolyline(lw_points)
    doc.saveas(CWD / "revcloud.dxf")


if __name__ == "__main__":
    main()

[mozman]

I change the default bulge value to 0.52...

If the first vertex matches the last vertex, the polyline is explicitly closed. This is not a problem for any CAD application - if so, it is not a true CAD application. 😊

[gswifort]

I didn't mean the first and last vertex of an explicitly closed polyline, but the "middle" vertices, e.g. for this example lw_points[10] == lw_points[11], lw_points[21] == lw_points[22] etc.
This is still not a problem for CAD applications, I just wanted to point out that it is an unnecessary duplication.

[mozman]

Got it!

[gswifort]

You can also add a comment in the docstring that the vertices should be given counterclockwise, otherwise the bulge will be inward (which is not the intended effect).
Alternatively, you can estimate whether most of the figure has the outer edge on the left or on the right (I don't know if you already have a function for this) - then you just need to set the bulge with a minus sign

[mozman]

I have a function to test if a polygon is clockwise or counter-clockwise oriented.

I will add such a test to revcloud.add_entity() and negate the bulge value for clockwise oriented polygons, this is accepted by BricsCAD and DWG TrueView. The low-level function revcloud.points() remains unchanged - maybe someone likes this shape better.

[mozman]

Example script to add a true REVCLOUD object: https://github.com/mozman/ezdxf/blob/master/examples/revcloud.py

These conditions must be met to create a true REVCLOUD representation:

• bulge value is 0.52056705
• LWPOLYLINE closed flag must be set
• XDATA "RevcloudProps" must be present

Whether the first vertex coincides with the last vertex or not is not important.

EDIT: moved module to ezdxf.revcloud as it can now do more than just render the required LWPOLYLINE points.