title: Metal -- skipping commandBuffer.present(drawable) to not display a frame?
body: <p>In my Metal app for macOS,  I have a situation where I only want to display the render results every so often.  I want to complete the rendering pass every frame, and save the drawable texture image to a file, but I only want to display the render every sixteenth frame or so.  I tried just skipping commandBuffer.present(drawable) when I don't want to display, but it is not working.  It just stops displaying new frames once I do that.  After skipping one call to commandBuffer.present(), it just doesn't display any new frames.  It does continue to run, however. </p>
  
  <p>Why would that happen?  Once I commit a command buffer, is it required for it to be presented?  </p>
  
  <p>If I can't get this to work, then I will try to render into an offscreen buffer for these frames I don't want displayed.  But it would be extra work and require more memory for the offscreen render buffer, so I'd rather just be able to use my regular onscreen render buffer if possible.</p>
  
  <p>Thanks!</p>