vnm_plot

A GPU-accelerated 2D time-series plotting library using OpenGL, with optional Qt Quick integration. _{function_plotter example}

CI Status

Job	Status	Notes
Linux (GitHub Actions)		Core + GLFW + Core+Text
Windows (GitHub Actions)		Core + GLFW + Core+Text
FreeBSD Core (Cirrus)		Core only
FreeBSD GLFW Example (Cirrus)		standalone_glfw
FreeBSD Core+Text (Cirrus)		Text enabled

Overview

vnm_plot renders time-series data using OpenGL geometry shaders. It supports Level-of-Detail (LOD) for handling large datasets. The renderer automatically selects an appropriate resolution based on the current zoom level.

The library uses a type-erased data interface (vnm::plot::Data_source + vnm::plot::Data_access_policy) so it can work with any sample type without templates in the rendering code.

Public header: include #include <vnm_plot/vnm_plot.h> only. It exposes core types unconditionally, and the Qt widgets when built with Qt (VNM_PLOT_WITH_QT).

Architecture

vnm_plot_core (standalone core library)
  -> Chrome_renderer (grid and axes)
  -> Series_renderer (data series)
  -> Text_renderer (labels)
  -> Font_renderer (MSDF glyphs)

vnm_plot (Qt wrapper)
  -> Plot_widget (QQuickFramebufferObject)
     -> Plot_renderer (GL thread)
        -> vnm_plot_core

• vnm_plot_core is the standalone rendering and data logic
• vnm_plot is the Qt Quick wrapper (QML-friendly Plot_widget)
• Plot_renderer runs on the GL thread and coordinates the sub-renderers
• Series_renderer handles lines, dots, and area fills with VBO management
• Chrome_renderer draws the grid and axes
• Font_renderer generates MSDF glyph atlases from FreeType

Usage

Plotting a Function

#include <vnm_plot/vnm_plot.h>

// plot_widget is a vnm::plot::Plot_widget* from QML or C++
// Create data source and generate samples
auto source = std::make_shared<vnm::plot::Function_data_source>();
source->generate([](double x) { return std::sin(x); }, 0.0, 10.0, 1000);

// Create series
auto series = std::make_shared<vnm::plot::series_data_t>();
series->id = 0;
series->data_source = source;
series->style = vnm::plot::Display_style::LINE;
series->color = glm::vec4(0.2f, 0.6f, 1.0f, 1.0f);

// Set up access policy
auto policy = vnm::plot::make_function_sample_policy();
series->access = policy;

// Add to widget
plot_widget->add_series(series->id, series);

QML Quickstart

Register the type in C++:

#include <vnm_plot/vnm_plot.h>

qmlRegisterType<vnm::plot::Plot_widget>("VnmPlot", 1, 0, "PlotWidget");

Use it in QML:

import VnmPlot 1.0

PlotWidget {
    id: plot
    anchors.fill: parent
}

Custom Sample Types

Implement a vnm::plot::Data_access_policy to tell the renderer how to read your samples:

struct my_sample_t {
    double timestamp;
    float  value;
    float  low;
    float  high;
};

vnm::plot::Data_access_policy make_my_policy() {
    vnm::plot::Data_access_policy p;
    p.get_timestamp = [](const void* s) {
        return static_cast<const my_sample_t*>(s)->timestamp;
    };
    p.get_value = [](const void* s) {
        return static_cast<const my_sample_t*>(s)->value;
    };
    p.get_range = [](const void* s) {
        auto* sample = static_cast<const my_sample_t*>(s);
        return std::make_pair(sample->low, sample->high);
    };
    p.sample_stride = sizeof(my_sample_t);
    return p;
}

// Assign policy to a series
auto series = std::make_shared<vnm::plot::series_data_t>();
series->access = make_my_policy();

Display Styles

• DOTS - points
• LINE - connected line
• AREA - filled area
• COLORMAP_AREA - area colored by auxiliary metric
• Combinations: DOTS_LINE, LINE_AREA, DOTS_LINE_AREA

Building

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build

Qt 6 (Core, Gui, Quick, OpenGL) is optional. The build fetches glm, glatter, FreeType, and msdfgen if they are not already available as targets.

To build the standalone core library only:

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release -DVNM_PLOT_BUILD_QT=OFF
cmake --build build

To disable text rendering (skips FreeType + msdfgen):

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release -DVNM_PLOT_ENABLE_TEXT=OFF
cmake --build build

Examples

Enable examples with:

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release -DVNM_PLOT_BUILD_EXAMPLES=ON
cmake --build build

• vnm_plot_hello - renders a sine wave using Function_data_source
• function_plotter - multiple functions, per-series styles, expression evaluation via mexce
• standalone_glfw - standalone core validation example using GLFW

function_plotter depends on mexce. You can point at a local checkout by configuring with -DMEXCE_LOCAL_PATH=....

Configuration

Customize rendering via Plot_config:

vnm::plot::Plot_config config;
config.dark_mode = true;
config.line_width_px = 2.0;
config.auto_v_range_mode = vnm::plot::Auto_v_range_mode::VISIBLE;
config.format_timestamp = [](double ts, double range) {
    return my_format_time(ts, range);
};
plot_widget->set_config(config);

Integration

As a subdirectory:

add_subdirectory(vnm_plot)
target_link_libraries(your_app PRIVATE vnm_plot::core)      # standalone core library
# target_link_libraries(your_app PRIVATE vnm_plot::vnm_plot) # Qt wrapper

Via FetchContent:

include(FetchContent)
FetchContent_Declare(vnm_plot
    GIT_REPOSITORY https://github.com/imakris/vnm_plot.git
    GIT_TAG        1.0.4
)
FetchContent_MakeAvailable(vnm_plot)
target_link_libraries(your_app PRIVATE vnm_plot::core)      # standalone core library
# target_link_libraries(your_app PRIVATE vnm_plot::vnm_plot) # Qt wrapper

Requirements

• OpenGL 4.3+ with geometry shader support and GL_ARB_gpu_shader_int64
• Qt 6.2+ (only required for the Qt wrapper target)

Scope

vnm_plot is a time-series plotter. It does not support 3D, scatter plots, pie charts, bar charts, histograms, or built-in legends/annotations.

License

BSD-2-Clause