title: Is it possible to drop a triangle from being rendered using vertex shaders?
body: <p>In a pixel shader you can discard a pixel but I would imagine even a fast-fail shader called for every pixel takes a non-trivial time? Is there any way a vertex shader can discard an entire triangle... I am fairly sure a VS <em>can't</em> access the primitive but are there any tricks  by which we can get the same result?</p>
  
  <p>Talking SM 3.0 here - for completeness discussion on newer versions is welcome.</p>