title: Problems caused by depth-stencil buffer created by default
body: <p>I'm learning from a sample in DirectX SDK on shadow map. This sample created a stencil surface during initialization, and says:</p>
  
  <pre><code> Create the depth-stencil buffer to be used with the shadow map
  
   We do this to ensure that the depth-stencil buffer is large
   enough and has correct multisample type/quality when rendering
   the shadow map.  The default depth-stencil buffer created during
   device creation will not be large enough if the user resizes the
   window to a very small size.  Furthermore, if the device is created
   with multisampling, the default depth-stencil buffer will not
   work with the shadow map texture because texture render targets
   do not support multisample.
  </code></pre>
  
  <p>What does this mean? I tried to comment the statements which creates and operates on the stencil buffer, then I got quite instable results: if I make the window greater, the shadow works well, while the shadow stops to move when I make the window much smaller.
  Does anyone can explain this to me? Thank you very much!!!</p>