SFML community forums

Help => Graphics => Topic started by: merl on October 09, 2016, 09:44:22 pm

Title: SFML Graphics module with OpenGL 3.3+
Post by: merl on October 09, 2016, 09:44:22 pm

Hello guys, I want to use the SFML Graphics module for 2D stuff along with OpenGL 3.3+ for 3D stuff. The RenderWindow constructor gives me a 4.5 context.
The problem is that I can either draw my 3D stuff or the 2D stuff but it does not work together. From the tutorial I understand that the graphics module depends on OpenGL legacy functions so I set the context attributeFlags to Default. Is that right?

window creation:

sf::ContextSettings settings;
settings.depthBits = 24;
settings.stencilBits = 8;
settings.attributeFlags = sf::ContextSettings::Default;
sf::RenderWindow window(sf::VideoMode(800, 600, 32), "OpenGL", sf::Style::Titlebar | sf::Style::Close, settings);

main loop for 3D:

while (running)
{
        sf::Event windowEvent;
        while (window.pollEvent(windowEvent))
        {
                switch (windowEvent.type)
                {
                case sf::Event::Closed:
                        running = false;
                        break;
                }
        }
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        window.display();
}

window.close();

this works fine.


main loop for 2D:

sf::Texture tex;
tex.loadFromFile("test.png");
sf::Sprite sprite;
sprite.setTexture(tex);

while (running)
{
        sf::Event windowEvent;
        while (window.pollEvent(windowEvent))
        {
                switch (windowEvent.type)
                {
                case sf::Event::Closed:
                        running = false;
                break;
                        }
        }
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT); // is this equivalent to window.clear()?
        window.draw(sprite);
        window.display();
}

window.close();

this only works if i comment out all gl... calls except the glClear stuff. If I don't the window is either black or I get access violations :/

What I want to do is really:

while (running)
{
        sf::Event windowEvent;
        while (window.pollEvent(windowEvent))
        {
                switch (windowEvent.type)
                {
                case sf::Event::Closed:
                        running = false;
                        break;
                }
        }
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        window.pushGLStates();
        window.resetGLStates();
        window.draw(sprite);
        window.popGLStates();
        window.display();
}

window.close();

Unfortunately, this only gives me a black window. The full source is in the spoiler. I hope someone can help.
Thanks in advance :)

full source:

(click to show/hide)

// Link statically with GLEW
#define GLEW_STATIC

// Headers
#include <GL/glew.h>
#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>

// Shader sources
const GLchar* vertexSource =
"#version 150 core\n"
"in vec2 position;"
"void main()"
"{"
"    gl_Position = vec4(position, 0.0, 1.0);"
"}";
const GLchar* fragmentSource =
"#version 150 core\n"
"out vec4 outColor;"
"void main()"
"{"
"    outColor = vec4(1.0, 1.0, 1.0, 1.0);"
"}";

int main()
{
        sf::ContextSettings settings;
        settings.depthBits = 24;
        settings.stencilBits = 8;
        settings.attributeFlags = sf::ContextSettings::Default;

        sf::RenderWindow window(sf::VideoMode(800, 600, 32), "OpenGL", sf::Style::Titlebar | sf::Style::Close, settings);

        // Initialize GLEW
        glewExperimental = GL_TRUE;
        glewInit();

        // Create Vertex Array Object
        GLuint vao;
        glGenVertexArrays(1, &vao);
        glBindVertexArray(vao);
 
        // Create a Vertex Buffer Object and copy the vertex data to it
        GLuint vbo;
        glGenBuffers(1, &vbo);

        GLfloat vertices[] = {
                0.0f,  0.5f,
                0.5f, -0.5f,
                -0.5f, -0.5f
        };

        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

        // Create and compile the vertex shader
        GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vertexShader, 1, &vertexSource, NULL);
        glCompileShader(vertexShader);

        // Create and compile the fragment shader
        GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
        glCompileShader(fragmentShader);

        // Link the vertex and fragment shader into a shader program
        GLuint shaderProgram = glCreateProgram();
        glAttachShader(shaderProgram, vertexShader);
        glAttachShader(shaderProgram, fragmentShader);
        glBindFragDataLocation(shaderProgram, 0, "outColor");
        glLinkProgram(shaderProgram);
        glUseProgram(shaderProgram);

        // Specify the layout of the vertex data
        GLint posAttrib = glGetAttribLocation(shaderProgram, "position");
        glEnableVertexAttribArray(posAttrib);
        glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);

        sf::Texture tex;
        tex.loadFromFile("test.png");
        sf::Sprite sprite;
        sprite.setTexture(tex);

        bool running = true;
        while (running)
        {
                sf::Event windowEvent;
                while (window.pollEvent(windowEvent))
                {
                        switch (windowEvent.type)
                        {
                        case sf::Event::Closed:
                                running = false;
                                break;
                        }
                }
                glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
                glClear(GL_COLOR_BUFFER_BIT);
                glDrawArrays(GL_TRIANGLES, 0, 3);
                //window.pushGLStates(); these lines don't work :/
                //window.resetGLStates();
                //window.draw(sprite);
                //window.popGLStates();
                window.display();
        }
        window.close();

        return 0;
}

Title: Re: SFML Graphics module with OpenGL 3.3+
Post by: binary1248 on October 10, 2016, 01:43:46 am

SFML doesn't track 3.0+ OpenGL state (i.e. VAO, VBO, etc.). Make sure you reset all 3.0+ state back to their default values and call window.resetGLStates() before trying to draw with the SFML graphics module.

Title: Re: SFML Graphics module with OpenGL 3.3+
Post by: merl on October 10, 2016, 01:49:11 pm

Thanks, that worked for me. For anyone having similar problems here is my new main loop:

while (running)
{
        sf::Event windowEvent;
        while (window.pollEvent(windowEvent))
        {
                switch (windowEvent.type)
                {
                case sf::Event::Closed:
                        running = false;
                        break;
                }
        }
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        glBindVertexArray(vao); // this line is new
        glBindBuffer(GL_ARRAY_BUFFER, vbo); // this one as well
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glBindBuffer(GL_ARRAY_BUFFER, 0); // !! this one as well
        glBindVertexArray(0); // this one as well

        window.pushGLStates();
        window.resetGLStates();
        window.draw(sprite);
        window.popGLStates();

        window.display();
}