README
View SourceEAGL

Make it EAsier to work
with OpenGL in Elixir.
Overview
Most examples of working with OpenGL are written in C++ or C# (Unity). The purpose of the EAGL library is to:
- Make it easier to translate OpenGL tutorials and examples from resources like Learn OpenGL into Elixir.
- Provide basic helper functions to bridge the gap between idiomatic Elixir and OpenGL's state machine, using the Wings 3D Erlang source as a guide.
- Enable other libraries and apps to build on this one - e.g. there should be Unity-like tool for the BEAM.
The following are non-goals:
- Wrapping of the Erlang wx library
- A Shader DSL
- A UI layout/component library
- 3D mesh modelling (leave that to Wings 3D, Blender etc)
Quick Start
# Add to mix.exs
{:eagl, "~> 0.1.0"}
EAGL includes several examples to demonstrate its capabilities. Use the unified examples runner:
./priv/scripts/run_examples
═══════════════════════════════════════════════════════════════
EAGL Examples Menu
═══════════════════════════════════════════════════════════════
1) Math Example
Comprehensive example demonstrating all EAGL.Math functionality
2) Teapot Example
Draw a 3D teapot with Phong shading
LearnOpenGL Examples:
1. Getting Started:
3) 1.1 Hello Window
Basic window creation - Foundation of all OpenGL applications
4) 1.2 Hello Window Clear
Custom clear colors - Understanding OpenGL's state machine
5) 2.1 Hello Triangle
Your first triangle - Basic VAO/VBO and shader fundamentals
6) 2.2 Hello Triangle Indexed
Element Buffer Objects (EBO) - Basic indexed rectangle rendering
7) 2.3 Hello Triangle Exercise 1
Two Triangles Side by Side - Using glDrawArrays with 6 vertices
8) 2.4 Hello Triangle Exercise 2
Element Buffer Objects (EBO) - Rectangle using shared vertices
9) 2.5 Hello Triangle Exercise 3
Multiple Shader Programs - Two triangles with different colors
10) 3.1 Shaders Uniform
Uniform Variables - Animated triangle with time-based color changes
11) 3.2 Shaders Interpolation
Vertex Color Interpolation - Triangle with red, green, blue corners
12) 3.3 Shaders Class
Shader Abstraction - Clean code organization and reusable patterns
13) 3.4 Shaders Exercise 1
Upside-Down Triangle - Vertex transformation in shader
14) 3.5 Shaders Exercise 2
Horizontal Offset - Uniform-controlled triangle positioning
15) 3.6 Shaders Exercise 3
Position as Color - Visualizing coordinates as RGB values
16) 4.1 Textures
Basic Texture Mapping - Applying 2D images to geometry
...
═══════════════════════════════════════════════════════════════
Enter example number (1-17), 'q' to quit, or 'r' to refresh:
>
Usage
Math Operations
import EAGL.Math
# Vector operations
position = vec3(1.0, 2.0, 3.0)
direction = vec3(0.0, 1.0, 0.0)
result = vec_add(position, direction)
length = vec_length(position)
# Matrix transformations
model = mat4_translate(vec3(5.0, 0.0, 0.0))
view = mat4_look_at(
vec3(0.0, 0.0, 5.0), # eye
vec3(0.0, 0.0, 0.0), # target
vec3(0.0, 1.0, 0.0) # up
)
projection = mat4_perspective(radians(45.0), 16.0/9.0, 0.1, 100.0)
EAGL provides a comprehensive 3D math library based on GLM supporting:
- Vectors: 2D, 3D, 4D vector operations with constructor macros
- Matrices: 2x2, 3x3, 4x4 matrix operations with transformation functions
- Quaternions: Rotation representation, SLERP, and conversion functions
- Utilities: Trigonometry, interpolation, clamping, and geometric functions
- OpenGL Integration: All functions work with the tuple-in-list format required by Erlang's OpenGL bindings
Shader Management
import EAGL.Shader
# Compile and link shaders
{:ok, vertex} = create_shader(@gl_vertex_shader, "vertex.glsl")
{:ok, fragment} = create_shader(@gl_fragment_shader, "fragment.glsl")
{:ok, program} = create_attach_link([vertex, fragment])
# Set uniforms with automatic type detection
set_uniform(program, "model_matrix", model_matrix)
set_uniform(program, "light_position", vec3(10.0, 10.0, 5.0))
set_uniform(program, "time", :erlang.monotonic_time(:millisecond))
# Or set multiple uniforms at once
set_uniforms(program, [
model: model_matrix,
view: view_matrix,
projection: projection_matrix,
light_position: vec3(10.0, 10.0, 5.0),
light_color: vec3(1.0, 1.0, 1.0)
])
The uniform helpers (from Wings3D) automatically detect the type of EAGL.Math values, eliminating the need to manually unpack vectors or handle different uniform types:
vec2/3/4
→glUniform2f/3f/4f
mat2/3/4
→glUniformMatrix2fv/3fv/4fv
- Numbers →
glUniform1f/1i
- Booleans →
glUniform1i
(0 or 1)
Texture Management
import EAGL.Texture
import EAGL.Error
# Load texture from image file (requires optional stb_image dependency)
{:ok, texture_id, width, height} = load_texture_from_file("priv/images/eagl_logo_black_on_white.jpg")
# Or create procedural textures for testing
{:ok, texture_id, width, height} = create_checkerboard_texture(256, 32)
# Manual texture creation and configuration
{:ok, texture_id} = create_texture()
:gl.bindTexture(@gl_texture_2d, texture_id)
# Set texture parameters with atom-to-constant conversion
set_texture_parameters(
wrap_s: :repeat,
wrap_t: :repeat,
min_filter: :linear_mipmap_linear,
mag_filter: :linear
)
# Load pixel data with format handling
load_texture_data(width, height, pixel_data,
internal_format: :rgb,
format: :rgb,
type: :unsigned_byte
)
# Generate mipmaps and check for errors
:gl.generateMipmap(@gl_texture_2d)
check("After generating mipmaps")
# Use multiple textures
:gl.activeTexture(@gl_texture0)
:gl.bindTexture(@gl_texture_2d, texture1_id)
:gl.activeTexture(@gl_texture1)
:gl.bindTexture(@gl_texture_2d, texture2_id)
# Clean up
:gl.deleteTextures([texture_id])
EAGL provides meaningful texture abstractions rather than thin wrappers:
- Image Loading:
load_texture_from_file()
with automatic fallback to checkerboard patterns - Texture Creation:
create_texture()
returns{:ok, id}
tuples for error handling - Parameter Setting:
set_texture_parameters()
converts atoms to OpenGL constants - Data Loading:
load_texture_data()
handles format/type conversion with defaults - Procedural Textures:
create_checkerboard_texture()
generates test patterns - Graceful Degradation: Helpful warnings when optional dependencies aren't available
- Direct OpenGL: Use
:gl
functions directly for binding, mipmaps, and cleanup
Model Loading
import EAGL.Model
# Load OBJ file (with automatic normal generation if missing)
{:ok, model} = load_model_to_vao("teapot.obj")
# Render the model
:gl.bindVertexArray(model.vao)
:gl.drawElements(@gl_triangles, model.vertex_count, @gl_unsigned_int, 0)
Buffer Management
import EAGL.Buffer
# Create simple position-only VAO/VBO (convenience function)
vertices = [-0.5, -0.5, 0.0, 0.5, -0.5, 0.0, 0.0, 0.5, 0.0]
{vao, vbo} = create_position_array(vertices)
# Or create with custom attributes (general function)
{vao, vbo} = create_vertex_array(vertices, [
{0, 3, @gl_float, @gl_false, 0, 0} # position at location 0
])
# Clean up
delete_vertex_array(vao, vbo)
Error Handling
import EAGL.Error
# Check for OpenGL errors with context
check("After buffer creation") # Returns :ok or {:error, message}
# Get human-readable error string for error code
error_string(1280) # "GL_INVALID_ENUM"
# Check and raise on error (useful for debugging)
check!("Critical operation") # Raises RuntimeError if error found
Window Creation
EAGL provides flexible window creation with a clean, options-based API:
- Default Size: 1024x768 pixels (can be customized with
size:
option) - 2D Rendering (default): No depth buffer, suitable for triangles, sprites, UI elements
- 3D Rendering: Enables depth testing and depth buffer for proper 3D scene rendering
- Automatic ENTER Handling: Optional ENTER key handling for simple examples and tutorials
defmodule MyApp do
use EAGL.Window
import EAGL.Shader
import EAGL.Math
def run_example do
# For 2D rendering (triangles, sprites, UI) - uses default 1024x768 size
EAGL.Window.run(__MODULE__, "My 2D OpenGL App")
# For 3D rendering (models, scenes with depth)
EAGL.Window.run(__MODULE__, "My 3D OpenGL App", depth_testing: true)
# For tutorials/examples with automatic ENTER key handling
EAGL.Window.run(__MODULE__, "Tutorial Example", return_to_exit: true)
# Custom window size and options
EAGL.Window.run(__MODULE__, "Custom Size App", size: {1280, 720}, depth_testing: true, return_to_exit: true)
end
@impl true
def setup do
# Initialize shaders, load models, etc.
{:ok, initial_state}
end
@impl true
def render(width, height, state) do
# Your render function should handle clearing the screen
:gl.clearColor(0.2, 0.3, 0.3, 1.0)
# For 2D rendering (depth_testing: false, default)
:gl.clear(@gl_color_buffer_bit)
# For 3D rendering (depth_testing: true)
# :gl.clear(@gl_color_buffer_bit ||| @gl_depth_buffer_bit)
# Render your content here
:ok
end
@impl true
def cleanup(state) do
# Clean up resources
:ok
end
end
Requirements
- Elixir: 1.14 or later
- Erlang/OTP: 25 or later (with wx support - included in standard distributions)
- OpenGL: 3.3 or later (for modern shader support)
Platform-specific Notes
All Platforms
EAGL uses Erlang's built-in wx
module for windowing, which is included with standard Erlang/OTP installations. No additional GUI libraries need to be installed.
Linux
Ensure you have OpenGL drivers installed:
# Ubuntu/Debian
sudo apt-get install libgl1-mesa-dev libglu1-mesa-dev
# Fedora/RHEL
sudo dnf install mesa-libGL-devel mesa-libGLU-devel
macOS
OpenGL is included with macOS. No additional setup required.
Note: EAGL automatically detects macOS and enables forward compatibility for OpenGL 3.0+ contexts, which is required by Apple's OpenGL implementation. This matches the behavior of the #ifdef __APPLE__
code commonly found in OpenGL tutorials.
Windows
OpenGL is typically available through graphics drivers. If you encounter issues, ensure your graphics drivers are up to date.
Installation
Clone the repository:
git clone https://github.com/yourusername/eagl.git cd eagl
Install dependencies:
mix deps.get
Compile the project:
mix compile
Run tests to verify everything works:
mix test
Try the examples:
./priv/scripts/run_examples
Project Structure
lib/
├── eagl/ # Core EAGL modules
│ ├── buffer.ex # VAO/VBO helper functions
│ ├── const.ex # OpenGL constants
│ ├── error.ex # Error checking and reporting
│ ├── math.ex # GLM-style math library
│ ├── model.ex # 3D model management
│ ├── obj_loader.ex # Wavefront OBJ parser
│ ├── shader.ex # Shader compilation
│ ├── window.ex # Window management
│ └── window_behaviour.ex # Window callback behavior
├── examples/ # Example applications
│ ├── math_example.ex # Math library demonstrations
│ ├── teapot_example.ex # 3D teapot rendering
│ └── learnopengl/ # LearnOpenGL tutorial ports
└── wx/ # wxWidgets constants
test/
├── eagl/ # Unit tests for EAGL modules
└── eagl_test.exs # Integration tests
priv/
├── models/ # 3D model files (.obj)
├── scripts/ # Convenience scripts
│ └── run_examples # Unified examples runner
└── shaders/ # GLSL shader files
└── learnopengl/ # LearnOpenGL tutorial shaders
Features
- ✅ Shader Management: Automatic compilation, linking, and error reporting
- ✅ Texture Management: Comprehensive texture creation, configuration, and loading with Wings3D-inspired helpers
- ✅ 3D Model Loading: Wavefront OBJ format with normals and texture coordinates
- ✅ Math Library: GLM-compatible vectors, matrices, quaternions with full OpenGL integration
- ✅ Buffer Helpers: Wings3D-inspired VAO/VBO management functions
- ✅ Error Handling: Comprehensive OpenGL error checking and reporting
- ✅ Window Management: Cross-platform window creation with wxWidgets
- ✅ Event Handling: Resize, close, and paint events
- ✅ Resource Cleanup: Automatic cleanup of OpenGL resources
- ✅ LearnOpenGL Examples: Direct ports of popular OpenGL tutorials
- ✅ Testing: Full test suite with OpenGL context mocking
Roadmap
The current focus is to:
- [ ] Port all the Learning OpenGL examples, adding helper functions when necessary
- [ ] Load common model types like GLTF
And in future:
- [ ] Be able to apply post-processing effects
- [ ] More extensive camera/lighting/material helpers
- [ ] Access to a physics engine
- [ ] Built-in GPU profiling tools
Community Contributions Welcome
- Documentation improvements and tutorials
- Additional LearnOpenGL tutorial ports
- Platform-specific optimizations
- Example applications and demos
Troubleshooting
Development Issues
Most of these are obvious, but it helps AI assistants remember how to get around the project.
Interactive Examples Hanging
Examples require user interaction (ESC key to exit). When running tests:
# Run only unit tests, exclude interactive examples
mix test test/eagl/ --exclude interactive
# Or set a timeout for interactive tests
mix test --timeout 10000
IEx Session Conflicts
If stuck in an IEx session when trying to run mix commands:
# Press 'a' to abort the IEx session, then run your command
# Example: after getting stuck, press 'a' then run:
mix compile
BREAK Prompt in IEx
If you encounter an unexpected error in IEx and see a BREAK: (a)bort
prompt:
# Press 'a' to abort and exit the IEx session
# This commonly happens when OpenGL context errors occur
# After pressing 'a', you can run your mix commands normally
Test Timeouts
Interactive examples wait for ESC key presses and will timeout in CI:
- Use
@tag :interactive
for examples that require user input - CI automatically excludes these tests
- Local development can run them individually
Examples Runner Interactive Input
The examples runner script requires user input and cannot be automated:
# This will hang waiting for user input:
./priv/scripts/run_examples
# Piping input incorrectly will also hang:
echo "16" | ./priv/scripts/run_examples # WRONG - hangs waiting for ENTER
# To test examples programmatically, run them directly:
mix run -e "EAGL.Examples.Math.run_example()"
timeout 5s mix run -e "EAGL.Examples.Teapot.run_example()"
# If you need to script the examples runner, use proper input format:
printf "16\nq\n" | timeout 10s ./priv/scripts/run_examples
Design Philosophy
EAGL focuses on meaningful abstractions rather than thin wrappers around OpenGL calls:
✅ Provide When Valuable
- Error handling patterns:
{:ok, result}
tuples and comprehensive error checking - Type conversions: Atoms to OpenGL constants (
set_texture_parameters(wrap_s: :repeat)
) - Sensible defaults: Reduce boilerplate with common parameter combinations
- Complex operations: Multi-step procedures like shader compilation and linking
- Data transformations: Converting Elixir data structures to OpenGL formats
- Procedural generation: Built-in patterns like checkerboard textures for testing
❌ Avoid Thin Wrappers
- Simple OpenGL calls: Use
:gl.bindTexture()
,:gl.generateMipmap()
directly - One-line functions: Don't wrap functions that only add
check()
calls - State management: Let users manage OpenGL state explicitly when appropriate
🎯 User Experience
- Import what you need:
import EAGL.Error
for explicit error checking - Call OpenGL directly: When EAGL doesn't add substantial value
- Mix and match: Use EAGL helpers alongside direct OpenGL calls seamlessly
This philosophy keeps the API clean, focused, and educational while providing real value where it matters most.
Contributing
- Fork the repository
- Create a feature branch (
git checkout -b feature/amazing-feature
) - Commit your changes (
git commit -m 'Add amazing feature'
) - Push to the branch (
git push origin feature/amazing-feature
) - Open a Pull Request
License
This project is licensed under the MIT License - see the LICENSE file for details.
Acknowledgments
- Learn OpenGL for excellent OpenGL tutorials
- Wings3D for inspiration and helper function patterns - the name EAGL(e) is a tip of the hat to this project
- The Erlang/OTP team for wxWidgets bindings
- The Elixir community for inspiration and support, particularly the Elixir Sydney/Australia User Group
- Cursor and Claude Sonnet for giving me the patience to get to running code and port the Learning OpenGL examples