title: how to control the rotation of the scene using track ball control using three.js
body: <p>I am constructing the building in 3D using three.js and webgl , i had placed the plane , sky , building on the plane , i had used TrackballControls to rotate the camera - it works perfect for zoom , pan but the plan rotates upside down , since i am constructing floor planner , i dont want to show the down side , I tried using OrbitControls and fixed rotation for this ,but the panning and zooming options are not flexible as TrackballControls 
  Below are my code for TrackballControls</p>
  
  <pre><code>   `controls = new THREE.TrackballControls( camera );  
      controls.userPan = true;
      controls.userPanSpeed = 0.0;        
      controls.userZoom  = true;
      controls.userZoomSpeed  = 2.0;      
      controls.userRotate  = true;
      controls.userRotateSpeed  = 1.0;
      controls.minDistance = 1.0; // how far can you zoom in
      controls.maxDistance = 1500.0; // how far can you zoom out      
      controls.maxPolarAngle = Math.PI *0.495;        
      controls.minPolarAngle = Math.PI/8;
      controls.rotation = Math.PI / 12;
      controls.minPolarAngle =  Math.PI *0.495;` 
  </code></pre>
  
  <p>and for OrbitControls</p>
  
  <pre><code>   `controls = new THREE.OrbitControls( camera );       
      controls.userPan = true;
      controls.userPanSpeed = 0.0;        
      controls.userZoom  = true;
      controls.userZoomSpeed  = 2.0;      
      controls.userRotate  = true;
      controls.userRotateSpeed  = 2.0;
      controls.minDistance = 1.0; // how far can you zoom in
      controls.maxDistance = 1500.0; // how far can you zoom out      
      controls.maxPolarAngle = Math.PI * 0.495;`
  </code></pre>
  
  <p>I feel TrackballControls is userfriendly , but need to fix the rotation alone , can any one guide me.
  Thanks in advance</p>