Thread: OpenGL texture rendering using SDL2 surfaces

Hi there, I'm relatively new to SDL2/OpenGL stuff, and I wanted to render
a textured quad. It seems like you can use SDL2 surfaces to create these
textures so that's what I went out and tried. In the end, I did not get any
errors, but the quad just appeared white, and had no texture. I was hoping
that any of you may have a clue to whats going wrong.

Code:

#include "graphics.h"

SDL_Window* graphics_window = NULL;
SDL_GLContext graphics_context;




// Textures
typedef struct graphics_texture {
    char* image;
    GLuint id;
    SDL_Surface* surface;
    int mode;
}graphics_texture;


graphics_texture noise = {"../media/noise.bmp", 0};


// Texture functions
int graphics_texturecreate(graphics_texture* texture) {
    texture->surface = SDL_LoadBMP(texture->image);
    if(texture->surface == NULL) {return 1;}


    glGenTextures(1, &texture->id);
    glBindTexture(GL_TEXTURE_2D, texture->id);


    texture->mode = GL_RGB;


    glTexImage2D(GL_TEXTURE_2D, 0, texture->mode, texture->surface->w, texture->surface->h, 0, texture->mode, GL_UNSIGNED_BYTE, texture->surface->pixels);
    
    SDL_FreeSurface(texture->surface);
    
    return 0;
}


int graphics_init(void) {
    // Initialize SDL2
    if(SDL_Init(SDL_INIT_VIDEO)) {
        printf("Could not initialize SDL2: %s\n", SDL_GetError());
        return 1;
    }


    // Create SDL2 window
    graphics_window = SDL_CreateWindow("SDL2 Window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, GRAPHICS_WIDTH, GRAPHICS_HEIGHT, SDL_WINDOW_OPENGL);
    if(graphics_window == NULL) {
        printf("Could not create window: %s\n", SDL_GetError());
        return 1;
    }
    
    // Initialize GL context
    graphics_context = SDL_GL_CreateContext(graphics_window);
    
    // Initialize OpenGL
    glClearColor(0.0, 0.0, 0.0, 1.0);
    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER,1);
    
    glViewport(0, 0, GRAPHICS_WIDTH, GRAPHICS_HEIGHT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, GRAPHICS_WIDTH, GRAPHICS_HEIGHT, 0, -1, 1);
    glMatrixMode(GL_MODELVIEW);


    // Textures
    glEnable(GL_TEXTURE_2D);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);


    if(graphics_texturecreate(&noise)) {
        printf("Could not create texture: %s\n", SDL_GetError());
        return 1;
    }


    return 0;
}


void graphics_render(void) {
    // Rendering
    glClear(GL_COLOR_BUFFER_BIT);
    
    // Draw a textured quad
    glBindTexture(GL_TEXTURE_2D, 0);
    glBegin(GL_QUADS);
        //glColor3ub(255, 0, 0);
        glTexCoord2f(0, 0);
        glVertex2i(100, 100);


        //glColor3ub(0, 255, 0);
        glTexCoord2f(0, 1);
        glVertex2i(100, 164);


        //glColor3ub(0, 0, 255);
        glTexCoord2f(1, 1);
        glVertex2i(164, 164);


        //glColor3ub(255, 0, 255);
        glTexCoord2f(1, 0);
        glVertex2i(164, 100);
    glEnd();
    
    // Present frame
    SDL_GL_SwapWindow(graphics_window);
}




void graphics_close(void) {
    // Clean up
    SDL_DestroyWindow(graphics_window);
    SDL_GL_DeleteContext(graphics_context);


    // Exit SDL2
    SDL_Quit();
}

keep in mind that I am still looking at what the best structure for my
code should be, I will probably still split up the texture stuff from the
regular stuff, and change something in my naming convention, but
until then, this is what I've got.

Thanks for the help all :]

I din't analize your code, but one thing you have to do is to tell SDL2 the type of context of OpenGL you are using. Nowadays OpenGL expects CORE PROFILE, but you are using COMPATIBLE PROFILE. So, add this call to your code:

Code:

SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY );