title: Multiple render targets given the same Direct2D factory
body: <p>I have to draw a lot of shapes by using Direct2D. I use a factory to create a render target I use to draw. Above these shapes I need to add others shapes without changing the previous (freehand drawing), but if I use the same render target I have to refresh the entire canvas (that is, redraw all the shapes), and this is not feasible because it is too slow.</p>
  
  <p>I need I solution that allows me to draw over the <em>static</em> shapes without continuously clear a draw all the canvas. I thought to create a new render target, by using the same factory, but this solution does not work for me (i.e. the new shapes are not displayed on the screen).</p>
  
  <p>Is there a solution that can fix this problem? As for example to draw the <em>static</em> shapes on a bitmap?</p>