EAGL

EAGL Logo

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:

The following are non-goals:

Quick Start

# Add to mix.exs
{:eagl, "~> 0.9.0"}

EAGL includes several examples to demonstrate its capabilities. Use the unified examples runner:

./priv/scripts/run_examples
════════════════════════════════════════════════════════════════
                         EAGL Examples Menu
════════════════════════════════════════════════════════════════

0. Non-Learn OpenGL Examples:
  01) Math Example - Comprehensive EAGL.Math functionality demo
  02) Teapot Example - 3D teapot with Phong shading

1. Learn OpenGL Getting Started Examples:

  Hello Window:     111) 1.1 Window    112) 1.2 Clear Colors

  Hello Triangle:   121) 2.1 Triangle  122) 2.2 Indexed    123) 2.3 Exercise1
                    124) 2.4 Exercise2 125) 2.5 Exercise3

  Shaders:          131) 3.1 Uniform   132) 3.2 Interpolation 133) 3.3 Class
                    134) 3.4 Exercise1 135) 3.5 Exercise2     136) 3.6 Exercise3

  Textures:         141) 4.1 Basic     142) 4.2 Combined      143) 4.3 Exercise1
                    144) 4.4 Exercise2 145) 4.5 Exercise3     146) 4.6 Exercise4

  Transformations:  151) 5.1 Basic     152) 5.2 Exercise1  153) 5.2 Exercise2

  Coordinate Systems: 161) 6.1 Basic   162) 6.2 Depth     163) 6.3 Multiple
                      164) 6.4 Exercise

  Camera:           171) 7.1 Circle    172) 7.2 Keyboard+DT 173) 7.3 Mouse+Zoom
                    174) 7.4 Camera Class 175) 7.5 Exercise1 (FPS) 176) 7.6 Exercise2 (Custom LookAt)

════════════════════════════════════════════════════════════════
Enter code (01, 02, 111-153), 'q' to quit, 'r' to refresh:
>

Usage

Math Operations

EAGL provides a comprehensive 3D math library based on GLM supporting:

Sigil Literals

EAGL provides three sigils for creating OpenGL data with compile-time validation and clean tabular formatting:

import EAGL.Math

# Matrix sigil (~m) - supports comments and automatic size detection
identity_4x4 = ~m"""
1.0  0.0  0.0  0.0
0.0  1.0  0.0  0.0
0.0  0.0  1.0  0.0
0.0  0.0  0.0  1.0
"""

transform_matrix = ~m"""
1.0  0.0  0.0  0.0
0.0  1.0  0.0  0.0
0.0  0.0  1.0  0.0
10.0 20.0 30.0 1.0  # Translation X, Y, Z (column-major: translation is in last column)
"""

# Vertex sigil (~v) - for raw vertex buffer data
triangle_vertices = ~v"""
# position      color
 0.0   0.5  0.0  1.0  0.0  0.0  # top vertex - red
-0.5  -0.5  0.0  0.0  1.0  0.0  # bottom left - green
 0.5  -0.5  0.0  0.0  0.0  1.0  # bottom right - blue
"""

# Index sigil (~i) - for element indices (must be integers)
quad_indices = ~i"""
0  1  3  # first triangle
1  2  3  # second triangle
"""

Vector and Matrix 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)

Camera System

EAGL provides a first-person camera system based on the LearnOpenGL camera class.

import EAGL.Camera
import EAGL.Math

# Create camera with default settings (origin, looking down -Z)
camera = Camera.new()

# Create camera with custom position and settings
camera = Camera.new(
  position: vec3(0.0, 5.0, 10.0),
  yaw: 180.0,
  pitch: -30.0,
  movement_speed: 5.0
)

# Get view and projection matrices for rendering
view = Camera.get_view_matrix(camera)
projection = mat4_perspective(radians(camera.zoom), aspect_ratio, 0.1, 100.0)

# Handle keyboard movement (WASD) - two approaches available:

# APPROACH 1: Simplified keyboard input (recommended)
# Process all WASD keys at once in tick handler for smoother movement
def handle_event(:tick, %{camera: camera, delta_time: dt} = state) do
  updated_camera = Camera.process_keyboard_input(camera, dt)
  {:ok, %{state | camera: updated_camera}}
end

# For FPS-style ground-based movement (constrains Y position)
def handle_event(:tick, %{camera: camera, delta_time: dt, ground_level: ground} = state) do
  updated_camera = Camera.process_fps_keyboard_input(camera, dt, ground)
  {:ok, %{state | camera: updated_camera}}
end

# APPROACH 2: Individual key processing (for custom key handling)
def handle_event({:key, key_code}, %{camera: camera, delta_time: dt} = state) do
  updated_camera = case key_code do
    ?W -> Camera.process_keyboard(camera, :forward, dt)
    ?S -> Camera.process_keyboard(camera, :backward, dt)  
    ?A -> Camera.process_keyboard(camera, :left, dt)
    ?D -> Camera.process_keyboard(camera, :right, dt)
    _ -> camera
  end
  {:ok, %{state | camera: updated_camera}}
end

# Handle mouse look and scroll zoom
def handle_event({:mouse_motion, x, y}, %{camera: camera, last_mouse: {last_x, last_y}} = state) do
  camera = Camera.process_mouse_movement(camera, x - last_x, last_y - y)
  {:ok, %{state | camera: camera, last_mouse: {x, y}}}
end

def handle_event({:mouse_wheel, _, _, _, wheel_delta}, %{camera: camera} = state) do
  camera = Camera.process_mouse_scroll(camera, wheel_delta)
  {:ok, %{state | camera: camera}}
end

Shader Management

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:

import EAGL.Shader

      # Compile and link shaders with type-safe shader types
      {:ok, vertex} = create_shader(:vertex, "vertex.glsl")
      {:ok, fragment} = create_shader(:fragment, "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)
])

Texture Management

EAGL provides meaningful texture abstractions:

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 type-safe keyword options
      set_texture_parameters(
        wrap_s: @gl_repeat,
        wrap_t: @gl_repeat,
        min_filter: @gl_linear_mipmap_linear,
        mag_filter: @gl_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])

Model Loading

Currently we only support the .obj format.

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

EAGL provides type-safe, buffer management with automatic stride/offset calculation and standard attribute helpers.

import EAGL.Buffer

# Simple position-only VAO/VBO (most common case)
vertices = ~v"""
-0.5  -0.5  0.0
 0.5  -0.5  0.0
 0.0   0.5  0.0
"""
{vao, vbo} = create_position_array(vertices)

# Multiple attribute configuration - choose your approach:
# Position + color vertices (6 floats per vertex: x,y,z,r,g,b)
position_color_vertices = ~v"""
# position      color
-0.5  -0.5  0.0  1.0  0.0  0.0  # vertex 1: position + red
 0.5  -0.5  0.0  0.0  1.0  0.0  # vertex 2: position + green  
 0.0   0.5  0.0  0.0  0.0  1.0  # vertex 3: position + blue
"""

# APPROACH 1: Automatic calculation (recommended for standard layouts)
# Automatically calculates stride/offset - no manual math required.
attributes = vertex_attributes(:position, :color)
{vao, vbo} = create_vertex_array(position_color_vertices, attributes)

# APPROACH 2: Manual configuration (for fine control or non-standard layouts)  
# Specify exactly what you want - useful for custom stride, non-sequential locations, etc.
attributes = [
  position_attribute(stride: 24, offset: 0),      # uses default location 0
  color_attribute(stride: 24, offset: 12)         # uses default location 1
]
{vao, vbo} = create_vertex_array(position_color_vertices, attributes)

# APPROACH 3: Custom locations (override defaults)
attributes = [
  position_attribute(location: 5, stride: 24, offset: 0),    # custom location 5
  color_attribute(location: 2, stride: 24, offset: 12)       # custom location 2
]
{vao, vbo} = create_vertex_array(position_color_vertices, attributes)

# Use automatic approach when:  - Standard position/color/texture/normal layouts
#                               - Sequential attribute locations (0, 1, 2, 3...)
#                               - Tightly packed (no padding between attributes)
#
# Use manual approach when:     - Custom attribute locations or sizes
#                               - Non-standard data types or normalization 
#                               - Attribute padding or unusual stride patterns
#                               - Need to match specific shader attribute locations

# Indexed geometry (rectangles, quads, models)
quad_vertices = ~v"""
 0.5   0.5  0.0  # top right
 0.5  -0.5  0.0  # bottom right
-0.5  -0.5  0.0  # bottom left
-0.5   0.5  0.0  # top left
"""
indices = ~i"""
0  1  3  # first triangle
1  2  3  # second triangle
"""
{vao, vbo, ebo} = create_indexed_position_array(quad_vertices, indices)

# Complex interleaved vertex data with multiple attributes
# Format: position(3) + color(3) + texture_coord(2) = 8 floats per vertex
interleaved_vertices = ~v"""
# x     y     z     r     g     b     s     t
-0.5  -0.5   0.0   1.0   0.0   0.0   0.0   0.0  # bottom left
 0.5  -0.5   0.0   0.0   1.0   0.0   1.0   0.0  # bottom right
 0.0   0.5   0.0   0.0   0.0   1.0   0.5   1.0  # top centre
"""

# Three standard attributes with automatic calculation
{vao, vbo} = create_vertex_array(interleaved_vertices, vertex_attributes(:position, :color, :texture_coordinate))

# Clean up resources
delete_vertex_array(vao, vbo)
delete_indexed_array(vao, vbo, ebo)  # For indexed arrays

Standard Attribute Helpers:

Two Configuration Approaches:

  1. Automatic Layout (recommended): vertex_attributes() assigns sequential locations (0, 1, 2, 3...) and calculates stride/offset automatically
  2. Manual Layout: Individual attribute helpers allow custom locations, stride, and offset for non-standard layouts

Key Benefits:

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:

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", enter_to_exit: true)
    
    # Custom window size and options
    EAGL.Window.run(__MODULE__, "Custom Size App", size: {1280, 720}, depth_testing: true, enter_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

  # Optional: Handle input and animation events
  @impl true
  def handle_event(event, state) do
    case event do
      # Keyboard input (W/A/S/D for camera movement, ESC to exit, etc.)
      {:key, key_code} ->
        # Handle keyboard input - see camera examples for WASD movement
        {:ok, state}
      
      # Mouse movement (for first-person camera look around)
      {:mouse_motion, x, y} ->
        # Handle mouse look - see camera examples for implementation
        {:ok, state}
      
      # Scroll wheel (for camera zoom)
      {:mouse_wheel, _x, _y, _wheel_rotation, wheel_delta} ->
        # Handle scroll zoom - positive/negative wheel_delta for zoom in/out
        {:ok, state}
      
      # 60 FPS tick for animations and updates
      :tick ->
        # Update animations, physics, camera movement, etc.
        {:ok, updated_state}
      
      _ ->
        {:ok, state}
    end
  end
end

Requirements

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 behaviour 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

  1. Clone the repository: 

    git clone https://github.com/yourusername/eagl.git
cd eagl

  2. Install dependencies: 

    mix deps.get

  3. Compile the project: 

    mix compile

  4. Run tests to verify everything works: 

    mix test

  5. Try the examples: 

    ./priv/scripts/run_examples

Project Structure

lib/
├── eagl/                   # Core EAGL modules
│   ├── buffer.ex           # VAO/VBO helper functions (516 lines)
│   ├── camera.ex           # First-person camera system (392 lines)
│   ├── const.ex            # OpenGL constants (842 lines)
│   ├── error.ex            # Error checking and reporting (110 lines)
│   ├── math.ex             # GLM-style math library (1494 lines)
│   ├── model.ex            # 3D model management (191 lines)
│   ├── obj_loader.ex       # Wavefront OBJ parser (456 lines)
│   ├── shader.ex           # Shader compilation (322 lines)
│   ├── texture.ex          # Texture loading and management (451 lines)
│   ├── window.ex           # Window management (597 lines)
│   └── window_behaviour.ex # Window callback behavior (66 lines)
├── 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
│   ├── buffer_test.exs     # Buffer management tests (577 lines)
│   ├── camera_test.exs     # Camera system tests (38 tests)
│   ├── error_test.exs      # Error handling tests (55 lines)
│   ├── math_test.exs       # Math library tests (1136 lines)
│   ├── model_test.exs      # Model loading tests (250 lines)
│   ├── obj_loader_test.exs # OBJ parser tests (141 lines)
│   ├── shader_test.exs     # Shader compilation tests (1033 lines)
│   └── texture_test.exs    # Texture management tests (449 lines)
└── 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

Roadmap

The current focus is to:

And in future:

Troubleshooting

Common Issues

Example Testing Timeouts

Examples use automatic timeouts for testing and will exit cleanly after the specified duration:

# Run all tests including automated example tests
mix test

# Run only unit tests if you want to skip example testing
mix test test/eagl/

# Run automated example tests specifically
mix test test/examples_test.exs

IEx Break Prompt

If you encounter an unexpected error in IEx and see a BREAK: (a)bort prompt, this indicates a crash in the BEAM VM. Enter 'a' to abort and return to the shell, then investigate the error that caused the crash.

Test Timeouts in CI

Examples now use automatic timeouts and run successfully in continuous integration environments:

Platform-Specific Issues

OpenGL Context Creation Failures

If you encounter context creation errors:

Missing Dependencies

If optional dependencies are missing, EAGL will show warnings but continue with fallback behaviour:

Contributing

We welcome contributions. Suggested contributions include:

Please read through these guidelines before submitting changes.

Development Setup

  1. Fork and clone the repository
  2. Install dependencies: mix deps.get
  3. Run tests to ensure everything works: mix test
  4. Try the examples: ./priv/scripts/run_examples

Code Standards

Style Guidelines

Testing Requirements

Documentation Standards

Design Philosophy

EAGL focuses on meaningful abstractions rather than thin wrappers around OpenGL calls:

✅ Provide Value

❌ Avoid Thin Wrappers

🎯 User Experience Goals

Submitting Changes

  1. Create a feature branch: git checkout -b feature/descriptive-name
  2. Make your changes following the style guidelines above
  3. Add or update tests for your changes
  4. Run the full test suite: mix test
  5. Update documentation if you've added new features
  6. Commit with clear messages: Use present tense, describe what the commit does
  7. Push your branch: git push origin feature/descriptive-name
  8. Open a Pull Request with:
    • Clear description of the changes
    • Reference to any related issues
    • Screenshots for visual changes
    • Test results if applicable

Questions and Support

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments