title: Fast-RCNN final bounding box
body: <p>I've been playing around with Fast-RCNN for a while, but still can't get some of the core mechanisms.</p>
  
  <p>In the tutorial slides (page 28 of <a href="http://tutorial.caffe.berkeleyvision.org/caffe-cvpr15-detection.pdf" rel="nofollow">http://tutorial.caffe.berkeleyvision.org/caffe-cvpr15-detection.pdf</a>), they have an example output with only one bounding box per object:</p>
  
  <p><a href="http://s22.postimg.org/7rbu05xbl/Screen_Shot_2015_12_04_at_2_19_57_PM.png" rel="nofollow">http://s22.postimg.org/7rbu05xbl/Screen_Shot_2015_12_04_at_2_19_57_PM.png</a></p>
  
  <p>Specifically, non-maximum suppression is performed on all region proposals(<a href="https://github.com/rbgirshick/fast-rcnn/blob/master/lib/fast_rcnn/test.py#L324" rel="nofollow">https://github.com/rbgirshick/fast-rcnn/blob/master/lib/fast_rcnn/test.py#L324</a>), but in my case it still contains tens of regions for each object in the image. </p>
  
  <p>My bounding boxes look like the following with threshold of 0.99:</p>
  
  <p><a href="http://s29.postimg.org/oc33ujgrb/foo.jpg" rel="nofollow">http://s29.postimg.org/oc33ujgrb/foo.jpg</a></p>
  
  <p>How and where are the bounding boxes for overlapping region finalized into one?</p>