Opengl undefined behavior

Question

I have been experiencing some strange behaviour using Opengl. I am doing something wrong, but I wasn't able to find out what it was.

I have HD Graphics 3000 accelerator and I have Opengl 3.0 installed on Ubuntu 14.04.

The problem is that nothing gets drawn sometimes especially when doing a small translation which should cause it to be visible. When rendering textures I get segmentation errors.

Here are important parts of the code:

Initiating SDL, creating opengl context, etc

if (SDL_Init(SDL_INIT_VIDEO) < 0) {
    exit(1);
}

SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);

SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);



mainwindow = SDL_CreateWindow("", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
    512, 512, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);


maincontext = SDL_GL_CreateContext(mainwindow);

glewInit();;


SDL_GL_SetSwapInterval(1);

Initiating opengl:

glClearColor(0.0,0.0,0.0,1.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();

gluPerspective(45,(double)width/(double)height,1,100.0);
glMatrixMode(GL_MODELVIEW);
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);  //we enable lighting, to make the 3D object to 3D
glEnable(GL_LIGHT0);
glEnable(GL_TEXTURE_2D);
float col[]= {1.0,1.0,1.0,1.0}; //light color is white
glLightfv(GL_LIGHT0,GL_DIFFUSE,col);
glEnable(GL_NORMALIZE);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

Rendering:

glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glClearColor ( 0.0, 0.0, 0.0, 1.0 );
glLoadIdentity();
glTranslatef(0,0,-5);

glColor3f(1,0,0);

glBegin(GL_TRIANGLES);
    glVertex3f(-1,-1,-5);
    glVertex3f(1,-1,-5);
    glVertex3f(0,1,-5);
glEnd();

I actually render some loaded models but even this triangle is not shown for some reason. If I render the models, when loading the textures a segmentation fault error happens when using the automatic routine provided by SOIL for loading images to opengl.

Any ideas? I also check for errors in opengl and also when initiating GLEW, but there aren't any.

Answer 1

Ok, the problem was that I worked with Opengl (call lightning, set view, etc) without initiating SDL and creating a context. Strangely, Opengl didn't call any errors.