Simple Cube

MrDaniel1 · September 12, 2016, 9:14pm

Hello,

Is it possible to use SDL2 to create a window and a cube with OpenGL?

You’d think this would be easy to find, but many examples use GLUT, GLEW or GLM.

Is there a pure implementation of creating a window, that is cross platform, and then rendering a cube?

I really feel dumb asking this as it’s a pretty basic demo.

Regards,

MrDaniel1 · September 12, 2016, 9:50pm

THIS IS HOW TO DO IT!!!

Code:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

#include <SDL2/SDL.h>
#include <SDL2/SDL_opengl.h>

/* Undefine this if you want a flat cube instead of a rainbow cube */
#define SHADED_CUBE

static SDL_GLContext ctx;
static SDL_Window* window;
/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. /
static void
quit(int rc)
{
if (ctx) {
/ SDL_GL_MakeCurrent(0, NULL); // doesn’t do anything */
SDL_GL_DeleteContext(ctx);
}
SDL_DestroyWindow( window );
SDL_Quit();
exit(rc);
}

static void
Render()
{
static float color[8][3] = {
{1.0, 1.0, 0.0},
{1.0, 0.0, 0.0},
{0.0, 0.0, 0.0},
{0.0, 1.0, 0.0},
{0.0, 1.0, 1.0},
{1.0, 1.0, 1.0},
{1.0, 0.0, 1.0},
{0.0, 0.0, 1.0}
};
static float cube[8][3] = {
{0.5, 0.5, -0.5},
{0.5, -0.5, -0.5},
{-0.5, -0.5, -0.5},
{-0.5, 0.5, -0.5},
{-0.5, 0.5, 0.5},
{0.5, 0.5, 0.5},
{0.5, -0.5, 0.5},
{-0.5, -0.5, 0.5}
};

/* Do our drawing, too. */
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glBegin(GL_QUADS);

#ifdef SHADED_CUBE
glColor3fv(color[0]);
glVertex3fv(cube[0]);
glColor3fv(color[1]);
glVertex3fv(cube[1]);
glColor3fv(color[2]);
glVertex3fv(cube[2]);
glColor3fv(color[3]);
glVertex3fv(cube[3]);

glColor3fv(color[3]);
glVertex3fv(cube[3]);
glColor3fv(color[4]);
glVertex3fv(cube[4]);
glColor3fv(color[7]);
glVertex3fv(cube[7]);
glColor3fv(color[2]);
glVertex3fv(cube[2]);

glColor3fv(color[0]);
glVertex3fv(cube[0]);
glColor3fv(color[5]);
glVertex3fv(cube[5]);
glColor3fv(color[6]);
glVertex3fv(cube[6]);
glColor3fv(color[1]);
glVertex3fv(cube[1]);

glColor3fv(color[5]);
glVertex3fv(cube[5]);
glColor3fv(color[4]);
glVertex3fv(cube[4]);
glColor3fv(color[7]);
glVertex3fv(cube[7]);
glColor3fv(color[6]);
glVertex3fv(cube[6]);

glColor3fv(color[5]);
glVertex3fv(cube[5]);
glColor3fv(color[0]);
glVertex3fv(cube[0]);
glColor3fv(color[3]);
glVertex3fv(cube[3]);
glColor3fv(color[4]);
glVertex3fv(cube[4]);

glColor3fv(color[6]);
glVertex3fv(cube[6]);
glColor3fv(color[1]);
glVertex3fv(cube[1]);
glColor3fv(color[2]);
glVertex3fv(cube[2]);
glColor3fv(color[7]);
glVertex3fv(cube[7]);

#else /* flat cube */
glColor3f(1.0, 0.0, 0.0);
glVertex3fv(cube[0]);
glVertex3fv(cube[1]);
glVertex3fv(cube[2]);
glVertex3fv(cube[3]);

glColor3f(0.0, 1.0, 0.0);
glVertex3fv(cube[3]);
glVertex3fv(cube[4]);
glVertex3fv(cube[7]);
glVertex3fv(cube[2]);

glColor3f(0.0, 0.0, 1.0);
glVertex3fv(cube[0]);
glVertex3fv(cube[5]);
glVertex3fv(cube[6]);
glVertex3fv(cube[1]);

glColor3f(0.0, 1.0, 1.0);
glVertex3fv(cube[5]);
glVertex3fv(cube[4]);
glVertex3fv(cube[7]);
glVertex3fv(cube[6]);

glColor3f(1.0, 1.0, 0.0);
glVertex3fv(cube[5]);
glVertex3fv(cube[0]);
glVertex3fv(cube[3]);
glVertex3fv(cube[4]);

glColor3f(1.0, 0.0, 1.0);
glVertex3fv(cube[6]);
glVertex3fv(cube[1]);
glVertex3fv(cube[2]);
glVertex3fv(cube[7]);

#endif /* SHADED_CUBE */

glEnd();

glMatrixMode(GL_MODELVIEW);
glRotatef(5.0, 1.0, 1.0, 1.0);

}

int
main(int argc, char *argv[])
{
int value;
int i, done;
SDL_DisplayMode mode;
SDL_Event event;
Uint32 then, now, frames;
int status;

//Initialize SDL
if( SDL_Init( SDL_INIT_VIDEO ) < 0 )
{
    printf( "SDL could not initialize! SDL_Error: %s\n", SDL_GetError() );
    return 1;
}

//Create window
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
window = SDL_CreateWindow
(
 "SDL AR Example",
 SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
 640, 480,
 SDL_WINDOW_OPENGL
 );

if( window == NULL )
{
    printf( "Window could not be created! SDL_Error: %s\n", SDL_GetError() );
    return 1;
}

//creating new context
ctx = SDL_GL_CreateContext(window);
SDL_GL_SetSwapInterval(1);


/* Set rendering settings */
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-2.0, 2.0, -2.0, 2.0, -20.0, 20.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glShadeModel(GL_SMOOTH);

/* Main render loop */
frames = 0;
then = SDL_GetTicks();
done = 0;
while (!done) {
    /* Check for events */
    ++frames;
    SDL_Event ev;
    while( SDL_PollEvent( &ev ) )
    {
        if( ( SDL_QUIT == ev.type ) ||
           ( SDL_KEYDOWN == ev.type && SDLK_ESCAPE == ev.key.keysym.sym ) )
        {
            break;
        }
    }
    int w, h;
    SDL_GL_MakeCurrent(window, ctx);
    SDL_GetWindowSize(window, &w, &h);
    glViewport(0, 0, w, h);
    Render();
    SDL_GL_SwapWindow(window);

}

/* Print out some timing information */
now = SDL_GetTicks();
if (now > then) {
    printf("%2.2f frames per second\n",
           ((double) frames * 1000) / (now - then));
}
quit(0);
return 0;

}

MrDaniel1 · September 12, 2016, 9:58pm