Ability to plot user-provided point line

[tzanio]

Overview

This PR adds an optional point line overlay (useful e.g. for reference curves), which can be toggled with Ctrl + l.

Points can be loaded from a file with the -pts command-line option, sent via socket with the pointline command, or specified in a GLVis scripts. The points line format is: number of points, followed by x y z coordinates.

The overlay appears as a red line connecting the given points.

Testing

Stand-alone with input from file

Use this circle_points.txt points file to run

./glvis -m ../mfem/data/star-q2.mesh -pts circle_points.txt -k "Aem"

and press Ctrl + l.

Server mode with input from file

Run

./glvis -pts circle_points.txt

then send a solution via socket, e.g. from mpirun -np 4 ./ex1p and press Ctrl + l.

Server mode with input by socket

Add sample points to the solution socket output in one of the examples, e.g. in ex1.cpp:

int sdim = mesh.SpaceDimension();
Vector bb_min, bb_max;
mesh.GetBoundingBox(bb_min, bb_max);
sol_sock << "pointline\n" << 2 << "\n"
          << bb_min(0) << ' ' << bb_min(1) << ' ' << ((sdim==2) ? 0.0 : bb_min(2)) << "\n"
          << bb_max(0) << ' ' << bb_max(1) << ' ' << ((sdim==2) ? 0.0 : bb_max(2)) << "\n"
          << flush;

start a server with ./glvis and then run ./ex1 -m ../data/escher.mesh.

The point line should appear by default and can be turned off/on with Ctrl + l.

In server mode, input by socket overrides input by file. In parallel, all ranks send point lines, but only the one from rank 0 is considered.

GLVis script

Use the files in this archive: test_pointline.zip to run

./glvis -run test_pointline.glvis

Press Space and rhe point line should appear; it can be turned off/on with Ctrl + l.

Potential improvements

• Add support for comments/blank lines in the points files
• Support multiple point lines (in the same or multiple files)
• Provide options to customize the style of the point line
• Smooth the curve with NURBS interpolation

[Copilot]

Pull request overview

This PR adds a user-provided “point line” overlay (red polyline) that can be toggled with Ctrl+l, with coordinates loadable from a points file (-pts), from the socket protocol (pointline command), or from GLVis scripts (pointline command).

Changes:

• Adds point-line state/storage (DataState::point_coords) and a shared parsing helper (ReadPointLine).
• Adds rendering support for the overlay across visualization scenes and a Ctrl+l toggle.
• Extends server/socket and script command handling to accept pointline, and adds -pts CLI option plus docs/changelog updates.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
lib/vsvector3d.cpp	Adds Ctrl+l help text and queues point line overlay in the 3D vector scene render list.
lib/vsvector.cpp	Adds Ctrl+l help text and queues point line overlay in the 2D vector scene render list.
lib/vssolution3d.cpp	Adds Ctrl+l help text and queues point line overlay in the 3D solution scene render list.
lib/vssolution.cpp	Adds Ctrl+l help text and queues point line overlay in the 2D solution scene render list.
lib/vsdata.hpp	Introduces point-line drawable/bool state and helper methods to prepare/toggle/render it.
lib/vsdata.cpp	Implements Ctrl+l behavior and point-line buffer creation and scene queueing.
lib/threads.hpp	Adds a new GLVis command type + storage for point line coordinates.
lib/threads.cpp	Implements pointline socket command parsing and execution wiring into the renderer.
lib/script_controller.cpp	Adds pointline support to the GLVis script command set.
lib/data_state.hpp	Adds point_coords to shared state and declares ReadPointLine.
lib/data_state.cpp	Implements ReadPointLine parsing helper and moves point_coords in move-assign.
glvis.cpp	Adds -pts option, loads point coordinates from file, and forwards them into server sessions.
README.md	Documents Ctrl+l toggle and references -pts.
CHANGELOG	Adds an entry documenting the new point line overlay feature.

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[tzanio]

@najlkin, @dylan-copeland, @v-dobrev and @camierjs -- all reviewer comments have been addressed and I tested that this works, can you take another look?

[tzanio]

One of the tests (glvis -run test_pointline.glvis) actually failed due to a bug (?) in CheckStreamIsComplex.

This was addressed in e8ce369 -- @najlkin, can you take a look?

[najlkin]

How about showing the overlay line by default when loaded from command line? That is expected behavior, I would say (why to load it otherwise...), and also it is better for headless rendering, so you do not need to send the Ctrl+l combination 🤔 . Actually, there seems to be no way to enter it by -k .

[najlkin]

One of the tests (glvis -run test_pointline.glvis) actually failed due to a bug (?) in CheckStreamIsComplex.

This was addressed in e8ce369 -- @najlkin, can you take a look?

Hmm, it has not happened to me, it is only with ZLib, I guess. Anyway, fixing it by the copy of StreamReader::CheckStreamIsComplex() is fine. Alternatively, it could be reused, but it is just a few lines, so not worth of it really.

[tzanio]

How about showing the overlay line by default when loaded from command line?

Done in 508df0d

it is only with ZLib

Despite the name of the class, this is not just for zlib -- the files used in the above script example are all text files (the zip file is just for easier download from GitHub).

[najlkin]

I know it is not just Zlib, but without MFEM compiled with Zlib, ifgzstream behaves more or less like regular fstream where you can save the position and go back and forth.

[tzanio]

Thanks @najlkin, @dylan-copeland, @camierjs and @v-dobrev!