OpenGL Vertex - Texture Mapping

Question

I have a mesh loaded by an obj file (wavefront), complete with normals and texture coordinates per face, and its relative texture available. In my C++ / OpenGL code (assignment for a computer graphics class) I bind correctly the texture, but fail at correctly mapping texture coordinates with face vertexes. Below I show the code for texture binding and the chain of calls to rasterize the object. I also show images for the expected result and the actual results (2 of them, one for each render setting). To be specific, it seems that the first render "tessellates" the plain image on the rasterized shape of the whole object, while the second maps the image once on the shape of the object.

What is going on here?

Bind procedure:

SDL_Surface *s = IMG_Load(filename.c_str());

glBindTexture(GL_TEXTURE_2D, textureIndex);
gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGB,
        s->w, s->h, GL_RGB, GL_UNSIGNED_BYTE, s->pixels);
glTexParameteri(GL_TEXTURE_2D,
        GL_TEXTURE_MAG_FILTER,
        GL_LINEAR );
glTexParameteri(GL_TEXTURE_2D,
        GL_TEXTURE_MIN_FILTER,
        GL_LINEAR_MIPMAP_LINEAR );

Raster procedure (pseudo code intended):

// gl pushMatrix, Traslation and rotations;
glPushMatrix();
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, textureIndex);
glColor3f(1,1,1);
glEnable(GL_TEXTURE_GEN_S);
glEnable(GL_TEXTURE_GEN_T);
glDisable(GL_LIGHTING);
glBegin(GL_TRIANGLES);
for (face f in faces) {
  glNormal3d(faceNormal.x, faceNormal.y, faceNormal.z);
  for (i = 0, i < 3, ++i) {
    glTexCoord3d(texturePoint[i].x, texturePoint[i].y, 0);
    glVertex3d(vertex[i].x, vertex[i].y, vertex[i].z);
  }
}
glEnd();
glPopMatrix();
// gl PopMatrix to exit from traslation / rotation context.

Answer 1

I see you use glEnable(GL_TEXTURE_GEN_S); but also use glTexCoord(...) to load coordinates. These are mutually exclusive features IIRC. If you are supplying your own texture coordinates you should not need to use glEnable(GL_TEXTURE_GEN_n).

Answer 2

for (i = 0, i < 3, ++i)
    glTexCoord3d(texturePoint[i].x, texturePoint[i].y, 0);
    glVertex3d(v[i]->x(), v[i]->y(), v[i]->z());

This code calls glTexCoord3d three times and glVertex3d only once. You need more braces around your for loop.

Answer 3

Your geometry may be prepared for Direct3D, which has texture space origin placed differently (top-left vs bottom-left corner). Try flipping either the texture's Y coordinates (i.e. load it from the bottom to the top), or the V texture coordinate (glTexCoord3d(texturePoint[i].x, 1.0f - texturePoint[i].y, 0);).