Why GL_CLAMP matters here?
===

I'm running [this example][1],

but changing:

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);

to:

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);


And I got a slightly different image at the top and right.

![enter image description here][2]

But as can seen from the code:

    glBegin(GL_QUADS);
    //lower left
    glTexCoord2f(0, 0); 
    glVertex2f(-1.0, -1.0);
    //upper left
    glTexCoord2f(0, 1.0);
    glVertex2f(-1.0, 1.0);
    //upper right
    glTexCoord2f(1.0, 1.0);
    glVertex2f(1.0, 1.0);
    //lower right_
    glTexCoord2f(1.0, 0); 
    glVertex2f(1.0, -1.0);
    glEnd();


The texture will not go out of range, why GL_CLAMP matters?


  [1]: http://stackoverflow.com/a/3585515/807893
  [2]: http://i.stack.imgur.com/jejfn.png