title: Efficient way of determining polygon intersection with bounding box
body: <p>I have a set of polygons, and I need to check whether they are intersecting with a given bounding box(rectangle).  What I am doing is, I am taking every vertex of polygon and checking whether it's inside bounding box or not.</p>
  
  <pre><code>If yes   
  return true   
  else   
  Now I am taking every vertex(i.e 4 vertices) of my bounding box and checking  whether it is inside polygon or not, 
  using  the algorithm from http://assemblysys.com/php-point-in-polygon-algorithm/
  if yes   
  return true  
  else
  return false(box and polygon are not intersecting)  
  </code></pre>
  
  <p>This way of approaching is taking too much time.  I want another algorithm which is faster than this.  I tried to search for an answer on Google but was not able to find anything.  I tried for finding code of mysql st_intersects() function on github but again I was unable to find that function code.  </p>
  
  <p>I know there are many algorithms but, because  I am new to this field I was unable to find algorithms,So I used the above approach.</p>