Texture rendering in OpenGL

Question

I know there are tons of questions about it, but I found nothing useful so far so, here I am.

I'm trying to render a texture which is attached to a wavefront .obj mesh. I continued to fail (somehow, it was like textures were not correctly loaded), so I wrote a simple example code to see where I was wrong. The sample code follows, and the texture is "correctly" loaded and rendered. However, there are some problems in the render itself: the image is incomplete / blurry / repeated / distorted. I will also post the expected result and the actual result.

Working on Linux Ubuntu 14.04, OpenGL 3.0 Mesa 10.5.9. Any idea of what is happening?

Texture (copyright Angryfly @ Turbosquid) and result on the right:

Sample code:

#include <math.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include<iostream>

int main(int argc, char* argv[]) {
    SDL_Init( SDL_INIT_VIDEO );
    SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 16 );
    SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
    // prepare the window
    SDL_Window *window = SDL_CreateWindow(argv[0], 0, 0,
            800, 600,
            SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);
    SDL_GLContext context = SDL_GL_CreateContext(window);
    // enable textures and bind a name (say 50)
    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, 50);

    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                     GL_LINEAR_MIPMAP_NEAREST );
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
    // load image with SDL
    SDL_Surface *s = IMG_Load("texture.png");
    // the following doesn't work (white space)
    //glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, s->w, s->h, 0, GL_RGB, GL_UNSIGNED_BYTE, s->pixels);
    gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGB, s->w, s->h, GL_RGB, GL_UNSIGNED_BYTE, s->pixels);

    glViewport(0, 0, 800, 600);
    glClearColor(1,1,1,1);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(70, 0.75, 0.2, 1000);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
    gluLookAt(0, 10, 0, 0, 0, 0, 1, 0, 0);

    glActiveTexture(50);
    // display texture as 2 triangles.
    glBegin(GL_TRIANGLES);
    glTexCoord2d(0,0); glVertex3d(-5, 0, -5);
    glTexCoord2d(0,1); glVertex3d(-5, 0, 5);
    glTexCoord2d(1,0); glVertex3d(5, 0, -5);

    glTexCoord2d(0,1); glVertex3d(-5, 0, 5);
    glTexCoord2d(1,0); glVertex3d(5, 0, -5);
    glTexCoord2d(1,1); glVertex3d(5, 0, 5);

    glEnd();
    glFinish();
    SDL_GL_SwapWindow(window);
    // wait for quit procedure
    SDL_Quit();
    return 0;

}

Answer 1

This type of artifact is a tell-tale sign that you've messed up your texture image format at the byte level. It's hard to tell what exactly is wrong, but it's something along the lines of bad pitch or a component layout mismatch.

Have a read of this wiki page and try again. glTexImage2D should work, keep trying until it does.