Weird strips with quads in OpenGL

Question

Everything is on the screenshot I just took... Basically, It does that even when there's no lighting enabled... Is it antialias related?

Screenshot : https://i.stack.imgur.com/N1G5E.png

@Axel, Here my code for a single cube :

glBegin(GL_QUADS);

glColor3f(r,g,b);

glNormal3f(0, 0, -1);
glVertex3f(position.x + radius, position.y + radius, position.z - radius);
glVertex3f(position.x + radius, position.y - radius, position.z - radius);
glVertex3f(position.x - radius, position.y - radius, position.z - radius);
glVertex3f(position.x - radius, position.y + radius, position.z - radius);

glNormal3f(0, 0, 1);
glVertex3f(position.x + radius, position.y + radius, position.z + radius);
glVertex3f(position.x + radius, position.y - radius, position.z + radius);
glVertex3f(position.x - radius, position.y - radius, position.z + radius);
glVertex3f(position.x - radius, position.y + radius, position.z + radius);

glNormal3f(-1, 0, 0);
glVertex3f(position.x - radius, position.y + radius, position.z + radius);
glVertex3f(position.x - radius, position.y - radius, position.z + radius);
glVertex3f(position.x - radius, position.y - radius, position.z - radius);
glVertex3f(position.x - radius, position.y + radius, position.z - radius);

glNormal3f(1, 0, 0);
glVertex3f(position.x + radius, position.y + radius, position.z + radius);
glVertex3f(position.x + radius, position.y - radius, position.z + radius);
glVertex3f(position.x + radius, position.y - radius, position.z - radius);
glVertex3f(position.x + radius, position.y + radius, position.z - radius);

glNormal3f(0, -1, 0);
glVertex3f(position.x + radius, position.y - radius, position.z + radius);
glVertex3f(position.x - radius, position.y - radius, position.z + radius);
glVertex3f(position.x - radius, position.y - radius, position.z - radius);
glVertex3f(position.x + radius, position.y - radius, position.z - radius);

glNormal3f(0, 1, 0);
glVertex3f(position.x + radius, position.y + radius, position.z + radius);
glVertex3f(position.x - radius, position.y + radius, position.z + radius);
glVertex3f(position.x - radius, position.y + radius, position.z - radius);
glVertex3f(position.x + radius, position.y + radius, position.z - radius);

glEnd();