🤖 Ability to plot user-provided point line

CHANGELOG

@@ -9,6 +9,15 @@
                              https://glvis.org
 
 
+Version 4.5.1 (development)
+===========================
+- Added 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'
+  option, sent via socket with the 'pointline' command, or specified in a GLVis
+  script. The overlay appears as a red line connecting the given points. The
+  points line format is: number of points, followed by x y z coordinates.
+
+
 Version 4.5 released on Feb 6, 2026
 ===================================
 

README.md

@@ -146,6 +146,7 @@ Key commands
   GLVis will use `SDL` to take screenshots in `bmp` format, which it will then
   convert to `png` if ImageMagick's `convert` tool is available.
 - <kbd>G</kbd> – 3D scene export to [glTF format](https://www.khronos.org/gltf)
+- <kbd>Ctrl</kbd> + <kbd>l</kbd> – Toggle point line (see `-pts` option)
 - <kbd>Ctrl</kbd> + <kbd>p</kbd> – Print to a PDF file using `gl2ps`. Other
   vector formats (SVG, EPS) are also possible, but keep in mind that the
   printing takes a while and the generated files are big.

glvis.cpp

@@ -12,6 +12,7 @@
 // GLVis - an OpenGL visualization server based on the MFEM library
 
 #include <limits>
+#include <array>
 #include <iostream>
 #include <fstream>
 #include <string>
@@ -157,7 +158,9 @@ class Session
 };
 
 void GLVisServer(int portnum, bool save_stream, bool fix_elem_orient,
-                 bool save_coloring, string plot_caption, bool headless = false)
+                 bool save_coloring, string plot_caption,
+                 std::vector<std::array<double,3>> point_coords,
+                 bool headless = false)
 {
    std::vector<Session> current_sessions;
    string data_type;
@@ -308,7 +311,7 @@ void GLVisServer(int portnum, bool save_stream, bool fix_elem_orient,
       }
 
       Session new_session(fix_elem_orient, save_coloring, plot_caption, headless);
-
+      if (!point_coords.empty()) { new_session.GetState().point_coords = point_coords; }
       constexpr int tmp_filename_size = 50;
       char tmp_file[tmp_filename_size];
       if (save_stream)
@@ -383,6 +386,7 @@ int main (int argc, char *argv[])
    const char *palette_name  = string_none;
    const char *window_title  = string_default;
    const char *font_name     = string_default;
+   const char *points_file   = string_none;
    int         portnum       = 19916;
    bool        persistent    = true;
    int         multisample   = GetMultisample();
@@ -493,6 +497,8 @@ int main (int argc, char *argv[])
    args.AddOption(&enable_hidpi, "-hidpi", "--high-dpi",
                   "-nohidpi", "--no-high-dpi",
                   "Enable/disable support for HiDPI at runtime, if supported.");
+   args.AddOption(&points_file, "-pts", "--points-file",
+                  "Points file: number of points, followed by x y z coordinates.");
 
    cout << endl
         << "       _/_/_/  _/      _/      _/  _/"          << endl
@@ -612,6 +618,21 @@ int main (int argc, char *argv[])
 
    GLVisGeometryRefiner.SetType(geom_ref_type);
 
+   // Load points file if specified (Ctrl+l to toggle)
+   if (points_file != string_none)
+   {
+      ifstream ifs(points_file);
+      if (!ifs)
+      {
+         cout << "Cannot open points file: " << points_file << endl;
+      }
+      else
+      {
+         int num_points = ReadPointLine(ifs, win.data_state.point_coords, cerr);
+         cout << "Loaded " << num_points << " points from " << points_file << endl;
+      }
+   }
+
    string data_type;
 
    // check for saved stream file
@@ -693,7 +714,9 @@ int main (int argc, char *argv[])
       std::thread serverThread{GLVisServer, portnum, save_stream,
                                win.data_state.fix_elem_orient,
                                win.data_state.save_coloring,
-                               win.plot_caption, win.headless};
+                               win.plot_caption,
+                               std::move(win.data_state.point_coords),
+                               win.headless};
 
       // Start message loop in main thread
       MainThreadLoop(win.headless, persistent);

lib/data_state.cpp

@@ -10,6 +10,9 @@
 // CONTRIBUTING.md for details.
 
 #include <cstdlib>
+#include <istream>
+#include <ostream>
+#include <string>
 
 #include "data_state.hpp"
 #include "visual.hpp"
@@ -36,6 +39,51 @@ class VectorExtrudeCoefficient : public VectorCoefficient
 QuadratureFunction* Extrude1DQuadFunction(Mesh *mesh, Mesh *mesh2d,
                                           QuadratureFunction *qf, int ny);
 
+
+int ReadPointLine(std::istream &in,
+                  std::vector<std::array<double,3>> &points,
+                  std::ostream &warn)
+{
+   points.clear();
+
+   int num_points;
+   in >> num_points;
+
+   if (num_points > 0)
+   {
+      points.reserve(num_points);
+   }
+
+   for (int j = 0; num_points < 0 || j < num_points; j++)
+   {
+      double x, y, z;
+      if (in >> x >> y >> z)
+      {
+         points.push_back({x, y, z});
+      }
+      else
+      {
+         warn << "Warning: failed reading point " << j << std::endl;
+         break;
+      }
+   }
+
+   const int read_points = (int) points.size();
+   if (read_points < 2)
+   {
+      warn << "Warning: ReadPointLine needs at least 2 points (got "
+           << read_points << ")" << std::endl;
+   }
+   else if (read_points < num_points)
+   {
+      warn << "Warning: ReadPointLine expected " << num_points
+           << " (got " << read_points << ")" << std::endl;
+   }
+
+   return read_points;
+}
+
+
 DataState &DataState::operator=(DataState &&ss)
 {
    internal = std::move(ss.internal);
@@ -49,6 +97,7 @@ DataState &DataState::operator=(DataState &&ss)
    save_coloring = ss.save_coloring;
    keep_attr = ss.keep_attr;
    cmplx_phase = ss.cmplx_phase;
+   point_coords = std::move(ss.point_coords);
 
    return *this;
 }

lib/data_state.hpp

@@ -15,6 +15,7 @@
 #include <map>
 #include <string>
 #include <memory>
+#include <array>
 #include <vector>
 #include <utility>
 #include <functional>
@@ -139,6 +140,7 @@ struct DataState
    bool save_coloring{false};
    bool keep_attr{false};
    double cmplx_phase{0.};
+   std::vector<std::array<double,3>> point_coords; // point line (from -pts)
 
    DataState() = default;
    DataState(DataState &&ss) { *this = std::move(ss); }
@@ -278,4 +280,11 @@ struct DataState
    { if (cgrid_f) { FindComplexValueRange(minv, maxv, vec2scal, scale); } else { minv = maxv = 0.; } }
 };
 
+/// Helper to read a point line file (num_points, followed by x y z coordinates)
+/// that is called in glvis.cpp and the 'pointline' commands in threads.cpp and
+/// script_controller.cpp.
+int ReadPointLine(std::istream &in,
+                  std::vector<std::array<double,3>> &points,
+                  std::ostream &warn);
+
 #endif // GLVIS_DATA_STATE_HPP

lib/script_controller.cpp

@@ -61,6 +61,7 @@ enum class Command
    Scale,
    Translate,
    PlotCaption,
+   PointLine,
    Headless,
    //----------
    Max
@@ -125,6 +126,7 @@ ScriptCommands::ScriptCommands()
    (*this)[Command::Scale]                = {"scale", "<scale>", "Set the scaling factor."};
    (*this)[Command::Translate]            = {"translate", "<x> <y> <z>", "Set the translation coordinates."};
    (*this)[Command::PlotCaption]          = {"plot_caption", "'<caption>'", "Set the plot caption."};
+   (*this)[Command::PointLine]            = {"pointline", "<num_points> <x y z>...", "Set point line overlay coordinates."};
    (*this)[Command::Headless]             = {"headless", "", "Change the session to headless."};
 }
 
@@ -843,6 +845,17 @@ bool ScriptController::ExecuteScriptCommand()
             MyExpose();
          }
          break;
+         case Command::PointLine:
+         {
+            int num_points = ReadPointLine(scr, win.data_state.point_coords, cerr);
+
+            win.vs->SetPointLineVisible(true);
+            win.vs->PreparePointLine();
+            MyExpose();
+
+            cout << "Script: pointline: " << num_points << " points" << endl;
+         }
+         break;
          case Command::Headless:
             cout << "The session cannot become headless after initialization" << endl;
             break;

lib/threads.cpp

@@ -11,6 +11,7 @@
 
 #include <array>
 #include <algorithm>
+#include <sstream>
 #include <thread>
 #include <vector>
 
@@ -240,6 +241,21 @@ int GLVisCommand::ColorbarNumberFormat(string formatting)
    return 0;
 }
 
+int GLVisCommand::PointLine(std::vector<std::array<double,3>> points)
+{
+   if (lock() < 0)
+   {
+      return -1;
+   }
+   command = Command::POINT_LINE;
+   point_coords = std::move(points);
+   if (signal() < 0)
+   {
+      return -2;
+   }
+   return 0;
+}
+
 int GLVisCommand::Pause()
 {
    if (lock() < 0)
@@ -839,6 +855,17 @@ int GLVisCommand::Execute()
          break;
       }
 
+      case Command::POINT_LINE:
+      {
+         cout << "Command: pointline: " << point_coords.size()
+              << " points" << endl;
+         win.data_state.point_coords = std::move(point_coords);
+         win.vs->SetPointLineVisible(true);
+         win.vs->PreparePointLine();
+         MyExpose();
+         break;
+      }
+
       case Command::QUIT:
       {
          thread_wnd->signalQuit();
@@ -916,6 +943,7 @@ enum class ThreadCommand
    AxisLabels,
    Pause,
    Autopause,
+   PointLine,
    //----------
    Max
 };
@@ -968,6 +996,7 @@ ThreadCommands::ThreadCommands()
    (*this)[ThreadCommand::AxisLabels]           = {"axis_labels", "'<x label>' '<y label>' '<z label>'", "Set labels of the axes."};
    (*this)[ThreadCommand::Pause]                = {"pause", "", "Stop the stream until space is pressed."};
    (*this)[ThreadCommand::Autopause]            = {"autopause", "<0/off/1/on>", "Turns off or on autopause."};
+   (*this)[ThreadCommand::PointLine]            = {"pointline", "<num_points> <x y z>...", "Set point line overlay coordinates."};
 }
 
 communication_thread::communication_thread(StreamCollection _is,
@@ -1594,6 +1623,27 @@ bool communication_thread::execute_one(std::string ident)
          }
       }
       break;
+      case ThreadCommand::PointLine:
+      {
+         // in parallel, use the point line data from rank 0
+         std::vector<std::array<double,3>> points;
+         int num_points = ReadPointLine(*is[0], points, cerr);
+
+         // assuming that all ranks have sent the same point data, perform dummy
+         // reads on the remaining ranks to sync parallel streams
+         std::vector<std::array<double,3>> dummy_points;
+         std::ostringstream dummy_stream;
+         for (size_t i = 1; i < is.size(); i++)
+         {
+            *is[i] >> ws >> ident; // 'pointline'
+            ReadPointLine(*is[i], dummy_points, dummy_stream);
+         }
+
+         glvis_command->PointLine(std::move(points));
+
+         cout << "Received " << num_points << " points" << endl;
+      }
+      break;
       case ThreadCommand::Max: //dummy
          break;
    }

lib/threads.hpp

@@ -12,6 +12,7 @@
 #ifndef GLVIS_THREADS_HPP
 #define GLVIS_THREADS_HPP
 
+#include <array>
 #include <mfem.hpp>
 #include <thread>
 #include <atomic>
@@ -62,6 +63,7 @@ class GLVisCommand
       LEVELLINES,
       AXIS_NUMBERFORMAT,
       COLORBAR_NUMBERFORMAT,
+      POINT_LINE,
       QUIT
    };
 
@@ -97,6 +99,7 @@ class GLVisCommand
    std::string   autopause_mode;
    std::string   axis_formatting;
    std::string   colorbar_formatting;
+   std::vector<std::array<double,3>> point_coords;
 
    // internal variables
    int autopause;
@@ -137,6 +140,7 @@ class GLVisCommand
    int Levellines(double minv, double maxv, int number);
    int AxisNumberFormat(std::string formatting);
    int ColorbarNumberFormat(std::string formatting);
+   int PointLine(std::vector<std::array<double, 3>> points);
    int Camera(const double cam[]);
    int Autopause(const char *mode);
    int Quit();