When using GL_LINEAR for texture filtering is there any way to make it clamp say it doesn't read texture coordinates outside the range you specify. For instance, if I specify texture coordinates that make a triangle like so:

* * e /
* e / |
e / * |
/ - - |

Then Whilst at the very edges of the texture it clamps along the long edge it blends the pixels labled 'e' in despite them being outside the specified triangle on the texture. Is there anyway to fix this so it treats the edge of every side the same whether they are backed onto the edge of the texture or not? I don't mind using extensions or what not.