OpenGL Samples (C & Erlang)

🚧 It's still in development.

This repository contains little OpenGL programs written in C with their counter-part written in Erlang and Elixir. They can be used as reference to write applications that use the the OpenGL bindings, and implicitly, the EGL binding. Note that they use GLFW for the windowing aspect.

The available samples are the following.

• colored-triangle - Shows a basic colored triangle.
• textured-cube - Shows a rotating textured cube.

Each sample is written to work with OpenGL 3.3, OpenGL 4.6, OpenGL ES 2.0 and OpenGL ES 3.2 (when possible). Note that OpenGL 4.6 on macOS is not available and ANGLE was used for OpenGL ES on both macOS and Windows.

OpenGL availability

• talk about libangle and how it enable OpenGL ES on macOS and Windows (it also provides EGL).

• talk about availability of OpenGL on macOS and Windows.

Compile and run C samples

Samples can only be compiled for one OpenGL version at a time. Therefore, first set the OPENGL_VERSION environment variable to one of the following values.

• opengl-3.0
• opengl-4.6
• opengl-es-2.0
• opengl-es-3.2

Then head to the samples/c folder and run make. All samples should be compiled.

Run them individually. For instance ./hello-world.

Compile and run Erlang samples

Samples can only be compiled for one OpenGL version at a time. Therefore, first set the OPENGL_VERSION environment variable to one of the following values.

• opengl-3.0
• opengl-4.6
• opengl-es-2.0
• opengl-es-3.2

Then head to the samples/erlang folder and run make. All samples should be compiled.

Run them individually. For instance ./hello-world.

Available samples

Several samples are provided with each attempting to reproduce a major feature of OpenGL. This section describes that.

The 'hello-world' sample

To be written.

Bar

To be written.

---

• OpenGL samples that I aim to have it ported to Erlang
• Help me showcase/test the code by having a reference

OpenGL ES 3.2

#include <stdio.h>
#include <stdlib.h>
#include <GLES3/gl3.h>
#include <EGL/egl.h>
#include <GLFW/glfw3.h>

glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_ES_API);

CC = gcc
CFLAGS = -Wall -Wextra -I/usr/include
LDFLAGS = -lglfw -lGLESv2 -lEGL

const char* vertex_shader_src = R"(
#version 320 es
layout(location = 0) in vec3 aPos;
layout(location = 1) in vec3 aColor;
out vec3 ourColor;
void main() {
    gl_Position = vec4(aPos, 1.0);
    ourColor = aColor;
}
)";

const char* fragment_shader_src = R"(
#version 320 es
precision mediump float;
in vec3 ourColor;
out vec4 FragColor;
void main() {
    FragColor = vec4(ourColor, 1.0);
}
)";

OpenGL 4.6

#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <GLFW/glfw3.h>

glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

CC = gcc
CFLAGS = -Wall -Wextra -I/usr/include
LDFLAGS = -lglfw -lGLEW -lGL

Project origin

During the development of the EGL and OpenGL bindings for Erlang, references in C needed to be used. Developing a large array of OpenGL bindings is challenging as they have to be cross-platform and also because each version of OpenGL has their specificities which we must test.

With those programs, we also set goals. Each program uses a specific feature of OpenGL, and if we can get it to reproduce this exact same behavior in Erlang, our task is complete.

In other words, they're sort of unit tests which allows test-driven development.

Of course, those programs are excellent candidates for source of reference after the bindings are complete and released to the public - They's why it's a public repo.

Files organization

You will find the C samples in the samples/c/ folder and their Erlang counter-parts in the samples/erlang/ folder. Each folder comes with a Makefile which allows you to conveniently compiles and run each sample.

Additionally, you will find the relevant quick reference cards as provided by Khronos Group in the cards/ folder.