BGFX Lines Rendering

1. Introduction

BGFX Lines is an open-source, general-purpose, multi-platform C++ library for rendering lines and polylines with variable thickness, custom caps, joins, and advanced visual effects—without relying on native API line primitives. Developed as part of my Bachelor’s degree final exam, the project leverages the bgfx cross-platform rendering library and demonstrates multiple algorithms for efficient and high-quality line rendering.

• No API line primitives used (fully custom)
• Supports variable thickness, caps, joins, borders
• Multiple CPU/GPU implementations including instancing and compute

2. Papers, Libraries, and Requirements

Papers & References

• bgfx: Cross-platform rendering library — https://github.com/bkaradzic/bgfx
• bx — https://github.com/bkaradzic/bx
• bimg (optional) — https://github.com/bkaradzic/bimg
• https://www.labri.fr/perso/nrougier/python-opengl/#rendering-lines
• https://www.yumpu.com/en/document/read/55443281/opengl-blueprint-rendering
• https://jcgt.org/published/0002/02/08/
• https://developer.nvidia.com/gpugems/gpugems2/part-iii-high-quality-rendering/chapter-22-fast-prefiltered-lines

Requirements

• C++17 or newer
• CMake ≥ 3.15
• Supported OS: Windows, Linux, macOS (others may work)
• GPU backend supported by bgfx (OpenGL, Direct3D, Vulkan, Metal)
• Shader model and compute support required for GPU-generated paths

3. Features

• Variable-width lines and polylines
• Caps (butt/round/square), joins (miter/bevel/round), borders/outlines
• Anti-aliased rendering strategies
• Five rendering approaches:
  • CPU-Generated: buffers generated on CPU, classical draw
  • GPU-Generated: buffers generated via compute shaders, then drawn
  • CPU Instancing: CPU data + instanced rendering
  • GPU Instancing: GPU compute + instanced rendering
  • Texture Instancing: instance data via texture buffer (TBO/SSBO)
• General-purpose, multi-platform, bgfx-based
• Modular design for easy integration into existing engines/tools

4. Installation and Usage

4.1. Getting the Source

git clone --recursive https://github.com/youruser/bgfx-lines.git
cd bgfx-lines

If you forgot --recursive, run:

git submodule update --init --recursive

4.2. Building

cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build --config Release

Artifacts:

• Static/dynamic library target(s) for integration
• Example/demo executables (if enabled)

Optional CMake options (create as needed):

• -DLINES_BUILD_EXAMPLES=ON
• -DLINES_BUILD_TESTS=ON

4.3. Minimal Usage Example

std::vector<lines::LinesVertex> points;
generatePointsInCube(points, 3, 100);
line = std::make_unique<lines::InstancingLines>(points);
line->settings().setThickness(5);
line->settings().setBorder(2);
line->settings().setAntialias(0);
line->settings().setLeftCap(lines::LineCap::TRIANGLE_CAP);
line->settings().setRigthCap(lines::LineCap::ROUND_CAP);
line->settings().setColorToUse(lines::LineColorToUse::PER_VERTEX_COLOR);
line->settings().setGeneralColor(lines::LinesVertex::COLOR(1, 0, 1, 1));


while (running) {
    // ... bgfx frame prep ...
    bgfx::touch(0);
    line->draw(0);
    bgfx::frame();
}
// Cleanup lines and bgfx...

See the examples/ folder for fully working samples per backend.

5. Results

Rendering of 500.000 lines visual effect and update each 1.0 sec

Rendering of a Graph using custom lines and polylines system with visual effects

Rendering of a model wireframe using custom lines with 5px thickness

6. Benchmark and Performance Analysis

Delta Time absulute value with static buffers (no-updates)	Delta Time compared with reference implementation with static buffers (no-updates)
Delta Time absulute value with dynamic buffers (updates)	Delta Time compared with reference implementation with dynamic buffers (updates)