Bad lighting behaviour (fixed pipeline)

Question

I'm trying to render an object (say cube) with OpenGL 1.1 (I know that doesn't makes sense nowadays, but I've to use this). Everything works fine until I try some lighting.

Here's the problem:

The Global variable set are:

static GLfloat light_position[] = {1.0, 1.0, 2*cZ.x , 0.0};   
// cZ.x is the minimum z of the mesh.  I know 
// this is at infinity, but don't work also with w=1.0

In the main function:

...
    glMatrixMode(GL_MODELVIEW);     // Select The Modelview Matrix
    glLoadIdentity();               // Reset The Modelview Matrix
    glEnable(GL_LIGHT0);
    glEnable(GL_LIGHTING);
    glShadeModel(GL_SMOOTH);        // Enable Smooth Shading

....

Drawing a mesh k

// While drawing mesh k

        GLfloat light_ambient[] = {COLOUR[k][0], COLOUR[k][1], COLOUR[k][2], 1.0}; 
        GLfloat light_diffuse[] = {COLOUR[k][0], COLOUR[k][1], COLOUR[k][2], 1.0};  
        glLightfv(GL_LIGHT0, GL_POSITION, light_position);
                glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
        glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);


....
        //This is a mesh, so will be drawn using triangles
        glBegin(GL_TRIANGLES);
        //Triangles will be defined by vertex indices in faces
        for (unsigned int i = 0; i<mesh->faces.size(); i++){

            int index1 = mesh->faces.at(i).x;
            int index2 = mesh->faces.at(i).y;
            int index3 = mesh->faces.at(i).z;
            glNormal3f(mesh->normals.at(i).x,mesh->normals.at(i).y,mesh->normals.at(i).z);
            glVertex3f(mesh->vertices.at(index1).x, mesh->vertices.at(index1).y, mesh->vertices.at(index1).z);
            glVertex3f(mesh->vertices.at(index2).x, mesh->vertices.at(index2).y, mesh->vertices.at(index2).z);
            glVertex3f(mesh->vertices.at(index3).x, mesh->vertices.at(index3).y, mesh->vertices.at(index3).z);
        }
        glEnd();

....

Whereas the normal are computed as:

    glm::vec3 currFace = m->faces.at(faceIndex);
    glm::vec3 vert1 = m->vertices.at(currFace.x);
    glm::vec3 vert2 = m->vertices.at(currFace.y);
    glm::vec3 vert3 = m->vertices.at(currFace.z);

    glm::vec3 side1 = (vert2 - vert1);
    glm::vec3 side2 = (vert3 - vert1);

    glm::vec3 normal = glm::cross(side1, side2);

    normal = glm::normalize(normal);

I'm really struggling to understand what's wrong, can you point me in the right direction?

EDIT: This happens similarly with the standford bunny (taken from standford repo, so it's well formed)

http://imgur.com/Z6225QG

Answer 1

Looking at your normals picture it looks like that more than not being shaded, some of your object faces are transparent.

I used to have a similar problem while learning OpenGL, in my case I forgot to enable DEPTH_TEST. You can do it simply adding this line to your GL init function function:

 glEnable(GL_DEPTH_TEST);

Give it a try