1D Arrangement on curve by efifogel · Pull Request #9608 · CGAL/cgal

efifogel · 2026-08-21T13:25:32Z

Summary of Changes

This new package is designed to construct, manipulate, and query one-dimensional arrangements embedded along continuous curves. While it recycles some old code, it uses newer idioms, such as property maps and C++17-style metaprogramming. The main class template is called Arrangement_on_curve_1. I also have 2 use cases:

It can be used to solve the following problem: Given a collection of 3D meshes and a curve c in 3D, find the maximal arcs that overlap with c, such that each arc does not intersect any mesh in its interior.
Compute the lower or upper envelope of 2D curves.

We have a package called "2D Envelopes", already in CGAL, which computes the lower or upper envelopes of 2D curves. I've reimplemented the code of this package using the new data structure Arrangement_on_curve_1. I also created a benchmark to ensure that there is no performance degradation. The branch, at this point, contains the new code. However, I may move it to a separate branch and introduce it in a separate PR after this one is fully merged.

The development is complete (code, tests, examples, and documentation).

Release Management

Affected package(s): Arrangement_on_curve_1
Issue(s) solved (if any):
Feature (if any): Features/1D Arrangements on Curves
Link to compiled documentation: The branch contains the full documentation.
License and copyright ownership: TAU

…ursively merges non-vertical curves.

afabri · 2026-08-24T14:06:24Z

/build:v0

github-actions · 2026-08-24T14:10:16Z

The documentation is built. It will be available, after a few minutes, here: https://cgal.github.io/9608/v0/Manual/index.html

afabri · 2026-08-24T14:26:05Z

+/*!
+\addtogroup PkgArrangementOnCurve1Ref
+\cgalPkgDescriptionBegin{1D Arrangements,PkgArrangementOnCurve1}
+\cgalPkgPicture{semicircle.png}


The teaser is too large.

Also I find it surprising to see a circular arc, while this seems not to be provided as functionality.

Can you suggest how ot shorten it?

1D arrangements on circular arcs are supported. As a matter of fact, the example arr_on_circle_segment.cpp demonstrates this. I added "; see Arrangement_on_curve_1/arr_on_circle_segment.cpp" near the figure.

afabri · 2026-08-24T14:27:05Z

+
+Given a set \f$\mathcal{P}\f$ of points on a curve, the <I>arrangement</I> \f$ {\mathcal A}({\mathcal P})\f$ is the subdivision of the curve induced by the points in \f$\mathcal{P}\f$ into maximally connected cells. The cells can be \f$0\f$-dimensional (<I>vertices</I>) or \f$1\f$-dimensional (<I>edges</I>).
+
+The class `Arrangement_on_curve_1<Traits>` encapsulates a data structure that maintains arrangements of points. It comes with a variety of algorithms that operate on 1D arrangements, such as point-location queries and overlay computations, which are implemented as peripheral classes or as free (global) functions.


Suggested change

The class `Arrangement_on_curve_1<Traits>` encapsulates a data structure that maintains arrangements of points. It comes with a variety of algorithms that operate on 1D arrangements, such as point-location queries and overlay computations, which are implemented as peripheral classes or as free (global) functions.

The class `CGAL::Arrangement_on_curve_1<Traits>` encapsulates a data structure that maintains arrangements of points. It comes with a variety of algorithms that operate on 1D arrangements, such as point-location queries and overlay computations, which are implemented as peripheral classes or as free (global) functions.

All free functions and types are defined under the namespace CGAL::Arrangement_on_curve_1. I added an explicit sentence to the User Manual stating this.

afabri · 2026-08-24T15:09:26Z

+- `CGAL::insert()`
+- `CGAL::locate()`
+- `CGAL::overlay()`
+- `CGAL::IO::read()`


The link goes to Arrangement_on_surface.

By the way there seem to be mistakes in the documentation of the concept AosInputFormatter. The default constructor does not have the right name.

I fixed the links (I think).
Regarding the mistakes in osInputFormatter, you are correct. As a matter of fact, the default constructor should not be listed. Instead, the page should include the statement:
\cgalRefines{DefaultConstructible}
The second constructor name should be fixed.
I'll fix it in a separate PR.

efifogel · 2026-08-25T09:23:30Z

Andreas, thanks for reviewing it.
I think that I've addressed all comments, except for teaser being too large, as I wasn't sure in what way.

afabri · 2026-08-25T09:32:18Z

These pictures are all 120x120 I think

efifogel · 2026-08-25T12:49:15Z

oh, it's the image size...right---I fixed it. ____ _ ____ _ /_____/_) o /__________ __ // (____ ( ( ( (_/ (_/-(-'_(/ _/

…

On Tue, 25 Aug 2026 at 12:32, Andreas Fabri ***@***.***> wrote: *afabri* left a comment (CGAL/cgal#9608) <#9608 (comment)> These pictures are all 120x120 I think — Reply to this email directly, view it on GitHub <#9608?email_source=notifications&email_token=ABVBNOCWIQ6DAU4QATTYW6T5LVMLPA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTKNBQHAZTSMZUGAY2M4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2KYZTPN52GK4S7MNWGSY3L#issuecomment-5408393401>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABVBNOEPNRQFAFCVT2RSYHT5LVMLPAVCNFSNUABEKJSXA33TNF2G64TZHMZDINRXG4ZTSMR3JFZXG5LFHM2TEMJUGUYDQNBUHCQXMAQ> . Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS <https://github.com/notifications/mobile/ios/ABVBNOBSD4FRF5W55SXUHZ35LVMLPA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTKNBQHAZTSMZUGAY2M4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2KUZTPN52GK4S7NFXXG> and Android <https://github.com/notifications/mobile/android/ABVBNOH4GULQYRV63DTFALL5LVMLPA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTKNBQHAZTSMZUGAY2M4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2K4ZTPN52GK4S7MFXGI4TPNFSA>. Download it today! You are receiving this because you authored the thread.Message ID: ***@***.***>

…Traits_1.h

afabri · 2026-08-27T11:54:41Z

/force-build:v0

github-actions · 2026-08-27T11:58:09Z

The documentation is built. It will be available, after a few minutes, here: https://cgal.github.io/9608/v0/Manual/index.html

afabri · 2026-08-27T12:13:23Z

@@ -0,0 +1,124 @@
+// Copyright (c) 2026 Tel-Aviv University (Israel).
+// All rights reserved.
+// This file is part of CGAL (www.cgal.org).


Suggested change

// This file is part of CGAL (www.cgal.org).

// This file is part of CGAL (www.cgal.org).

// $URL$

// $Id$

Must be added in several other header files as reported by the CI

These tags are historical artifacts left over from the SVN days.
I don't mind adding them, but it would be better to remove them from all files instead.

They get filled by scripts for the released tar balls, so they are used and useful.

I added them

efifogel added 30 commits May 25, 2026 14:32

1st revision

7f13d5c

Made more generic

92957af

Cleaned up

337480e

Added remove()

1693ece

Fixed and enhanced the overlay functionality

b9a7725

Fixed overlay observer

92dedd7

Added const

ed9704d

Reimplemented

3128e12

Reorganized

1b376d4

Cleaned up

53d8717

Updated

acfde60

Used shared_ptr to pass the geometry traits

2ac96ce

Introduced Ft_traits_1

2a28a36

Cleaned up

e1115a3

Updated

50f7532

Added user manual

d1857e1

Typo

483beb0

Used property maps

5c62aa5

1st revision

83f7b57

1st revision

7f5f3ab

1D Arrangements

316bcf3

Added Arrangement_on_curve_1

7f9f4c1

Added a minimal test

999856b

Fixed the doc and the package description

f880fb0

Fixed sentinel

38a8096

Fixed typo in directory name

552c8a5

Performance fixes

fcfd5bd

Cleaned up

11539a4

1st revision

6d606d3

Enhanced

3f65e20

efifogel added 6 commits August 13, 2026 10:58

Streamed line the different implementations of the procedure that rec…

e3052e0

…ursively merges non-vertical curves.

Updated

956f629

Documentation fixes

5f176f0

More documentation fixes

0a26dc1

More documentation fixes

e67696d

Introduced documentation for the topology traits

4a9aab4

afabri reviewed Aug 24, 2026

View reviewed changes

Comment thread Arrangement_on_curve_1/test/Arrangement_on_curve_1/CMakeLists.txt Outdated

Apply suggestion from @afabri

ab2ca17

afabri requested changes Aug 24, 2026

View reviewed changes

afabri reviewed Aug 24, 2026

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Comment thread Arrangement_on_curve_1/examples/Arrangement_on_curve_1/overlay_line_3.cpp Outdated

afabri reviewed Aug 24, 2026

View reviewed changes

efifogel added 3 commits August 25, 2026 11:54

Fixed several typos, namespace related errors, rephrasing, enc.

b967de0

DefaultConstructible

1e6cdfd

Moved IO under CGAL::Arrangement_on_curve_1 to match the namespace.

6ea54e0

Fixed teaser image

e9b8b62

efifogel and others added 3 commits August 25, 2026 15:54

Removed labels

b0bebc2

1st revision

2413753

Update Arrangement_on_curve_1/doc/Arrangement_on_curve_1/Concepts/Aoc…

ab59964

…Traits_1.h

afabri reviewed Aug 27, 2026

View reviewed changes

efifogel added 4 commits August 29, 2026 11:35

Fixed namespace

ce4d3bc

Added an entry for "1D Arrangement on Curves" package

5bd79ea

Added "// $URL$" and "// $Id$"

480cb20

Added "// $URL$" and "// $Id$"

bd746cb


		Given a set \f$\mathcal{P}\f$ of points on a curve, the <I>arrangement</I> \f$ {\mathcal A}({\mathcal P})\f$ is the subdivision of the curve induced by the points in \f$\mathcal{P}\f$ into maximally connected cells. The cells can be \f$0\f$-dimensional (<I>vertices</I>) or \f$1\f$-dimensional (<I>edges</I>).

		The class `Arrangement_on_curve_1<Traits>` encapsulates a data structure that maintains arrangements of points. It comes with a variety of algorithms that operate on 1D arrangements, such as point-location queries and overlay computations, which are implemented as peripheral classes or as free (global) functions.

	The class `Arrangement_on_curve_1<Traits>` encapsulates a data structure that maintains arrangements of points. It comes with a variety of algorithms that operate on 1D arrangements, such as point-location queries and overlay computations, which are implemented as peripheral classes or as free (global) functions.
	The class `CGAL::Arrangement_on_curve_1<Traits>` encapsulates a data structure that maintains arrangements of points. It comes with a variety of algorithms that operate on 1D arrangements, such as point-location queries and overlay computations, which are implemented as peripheral classes or as free (global) functions.

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efifogel commented Aug 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary of Changes

Release Management

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afabri commented Aug 24, 2026

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efifogel commented Aug 25, 2026

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afabri commented Aug 25, 2026

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efifogel commented Aug 25, 2026 via email

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efifogel commented Aug 21, 2026 •

edited

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