title: Clear single viewport in DirectX 10
body: <p>I am preparing to start on a C++ DirectX 10 application that will consist of multiple "panels" to display different types of information.  I have had some success experimenting with multiple viewports on one RenderTargetView.  However, I cannot find a definitive answer regarding how to clear a single viewport at a time.  These panels (viewports) in my application will overlap in some areas, so I would like to be able to draw them from "bottom to top", clearing each viewport as I go so the drawing from lower panels doesn't show through on the higher ones.  In DirectX 9, it seems that there was a Clear() method of the device object that would clear only the currently set viewport.  DirectX 10 uses ClearRenderTargetView(), which clears the entire drawing area, and I cannot find any other option that is equivalent to the way DirectX 9 did it.</p>
  
  <p>Is there a way in DirectX 10 to clear only a viewport/rectangle within the drawing area?  One person speculated that the only way may be to draw a quad in that space.  It seems that another possibility would be to have a seprate RenderTargetView for each panel, but I would like to avoid that as it requires other redundant resources, such as a separate depth/stencil buffers (unless that is a misunderstanding on my part).</p>
  
  <p>Any help will be greatly appreciated!  Thanks!</p>