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SFML - Part 5 - Shaders

This article is part of a tutorial dedicated to SFML. The reader may consult the other parts of the tutorial by following this link : SFML tutorial.

Introduction

This post presents how to create shaders with SFML. Example presented on this page has been prepared with the following software versions:

The following video is a preview of the result:

Example and source code

This example shows how to use shaders. Shaders are programs executed in the GPU (Graphics Processing Unit). The advantage is to release the main processor from this computation.

#include <SFML/Graphics.hpp>
#include <iostream>

// Examples from http://glslsandbox.com/
// Example 1 : mouse on fire
// Example 2 : scrolling of shapes
// Example 3 : cells
// Example 4 : fire
// Example 5 : moving circles
// Example 6 : smoke
// Example 7 : horizontal scrolling mountains
#define SHADER_FILENAME         "../example_001.frag"
//#define SHADER_FILENAME         "../example_002.frag"
//#define SHADER_FILENAME         "../example_003.frag"
//#define SHADER_FILENAME         "../example_004.frag"
//#define SHADER_FILENAME         "../example_005.frag"
//#define SHADER_FILENAME         "../example_006.frag"
//#define SHADER_FILENAME         "../example_007.frag"

#define     WINDOW_WIDTH    800
#define     WINDOW_HEIGHT   600

int main()
{

    // Create a non resizable window
    sf::RenderWindow window(sf::VideoMode(WINDOW_WIDTH, WINDOW_HEIGHT), "SFML Shader Example", sf::Style::Titlebar | sf::Style::Close);

    // Create a window size texture and a sprite for the shader
    sf::Texture tex;
    tex.create(WINDOW_WIDTH, WINDOW_HEIGHT);
    sf::Sprite spr(tex);

    // Create an load the shader from file
    sf::Shader shader;
    shader.loadFromFile(SHADER_FILENAME, sf::Shader::Fragment);
    if (!shader.isAvailable()) {
        std::cout << "The shader is not available\n";
        return -1;
    }

    // Set the resolution parameter (initial window size)
    shader.setParameter("resolution", sf::Vector2f(WINDOW_WIDTH , WINDOW_HEIGHT));

    // Use a timer to obtain the time elapsed
    sf::Clock clk;

   // Main loop
    while (window.isOpen()) {
        // Event handling
        sf::Event event;

        // Event loop (keyboard, mouse ...
        while (window.pollEvent(event))
        {
            // Close the window if a key is pressed or if requested
            if (event.type == sf::Event::Closed) window.close();

            // Exit the app when a key is pressed
            if (event.type == sf::Event::KeyPressed) window.close();
        }

        // Set the others parameters who need to be updated every frames (time and mouse)
        shader.setParameter("time", clk.getElapsedTime().asSeconds());
        sf::Vector2i mousePos = sf::Mouse::getPosition(window);
        shader.setParameter("mouse", sf::Vector2f(mousePos.x, mousePos.y - WINDOW_HEIGHT/2));

        // Draw the sprite with the shader on it
        window.clear();
        window.draw(spr, &shader);
        window.display();
    }

    return 0;
}

Download

Qt project, files, shaders and source codes can be downloaded for GitLab:

Source code on GitLab

See also


Last update : 03/15/2021