DS Log

In my blog, I delve into the world of programming web technologies, Linux, Unix-like, and graphic design using free tools on Linux.

Wednesday, February 19, 2025

OPENGL intro

OpenGL (Open Graphics Library) is a cross-platform, low-level graphics API (Application Programming Interface) used for rendering 2D and 3D vector graphics. It provides a set of functions that allow developers to create graphics applications, such as video games, simulations, and visualizations, by interacting with the graphics hardware. We will use Ubuntu or LinuxMint for this tutorial.

GLEW

GLEW (OpenGL Extension Wrangler Library). GLEW is a cross-platform library that helps manage OpenGL extensions and core functionality. It simplifies the process of accessing OpenGL features, especially extensions, which are not part of the core OpenGL specification.

Key Features of GLEW

Feature	Description
Extension Loading	GLEW provides a way to dynamically load OpenGL extensions at runtime. This is important because different graphics hardware and drivers may support different sets of OpenGL extensions. It allows you to check whether a specific extension or OpenGL version is supported by the current system.
Core OpenGL Functions	GLEW also provides access to core OpenGL functions, making it easier to write portable OpenGL code.
Cross-Platform	GLEW works on multiple platforms, including Windows, macOS, and Linux.
Automatic Initialization	GLEW automatically initializes itself and queries the available OpenGL extensions when you call glewInit().

GLFW

GLFW (Graphics Library Framework) is a cross-platform library designed to create windows, handle input (keyboard, mouse, joystick), and manage OpenGL contexts. It is commonly used in OpenGL applications to simplify the process of setting up a rendering environment.

Key Features of GLFW

Feature	Description
Window and Context Management	GLFW creates windows and OpenGL contexts, making it easier to set up a rendering environment. It supports multiple monitors and full-screen mode.
Input Handling	GLFW provides functions to handle keyboard, mouse, and joystick input. It supports callbacks for events like key presses, mouse movement, and window resizing.
Cross-Platform	GLFW works on Windows, macOS, and Linux, making it a popular choice for cross-platform OpenGL applications.
Integration with OpenGL	GLFW is designed to work seamlessly with OpenGL, allowing you to focus on rendering rather than platform-specific details.
Minimalistic and Lightweight	GLFW is simple to use and does not impose a heavy framework on your application.

Preparing system

We need to prepare our Linux system for development.
Check that your system supports OpenGL and that the necessary drivers are installed:

🚀 glxinfo | grep "OpenGL version"

If yes then let's install following packages:

🚀 sudo apt-get update
🚀 sudo apt-get install build-essential automake autoconf cmake git checkinstall pkg-config g++ libtool

Test program

Now open your favorite editor (use Geany) and save this to "test.c" file:

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

int main() {
    // Initialize GLFW
    if (!glfwInit()) {
        fprintf(stderr, "Failed to initialize GLFW\n");
        return -1;
    }

    // Set OpenGL version to 3.3 (core profile)
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    // Create a windowed mode window and its OpenGL context
    GLFWwindow* window = glfwCreateWindow(640, 480, "OpenGL Test", NULL, NULL);
    if (!window) {
        fprintf(stderr, "Failed to create GLFW window\n");
        glfwTerminate();
        return -1;
    }

    // Make the window's context current
    glfwMakeContextCurrent(window);

    // Initialize GLEW
    if (glewInit() != GLEW_OK) {
        fprintf(stderr, "Failed to initialize GLEW\n");
        return -1;
    }

    // Print OpenGL version
    printf("OpenGL Version: %s\n", glGetString(GL_VERSION));

    // Main loop
    while (!glfwWindowShouldClose(window)) {
        // Clear the screen to red
        glClearColor(1.0f, 0.0f, 0.0f, 1.0f); // Red background
        glClear(GL_COLOR_BUFFER_BIT);

        // Swap front and back buffers
        glfwSwapBuffers(window);

        // Poll for and process events
        glfwPollEvents();
    }

    // Clean up and exit
    glfwDestroyWindow(window);
    glfwTerminate();
    return 0;
}

To compile the code open terminal where your code is and type:

🚀 gcc test.c -o test -lglfw -lGLEW -lGL

If everything is compiled, run the binary:

🚀 ./test

posted by damirs @ February 19, 2025