Canvas 3d JS Library

This demo will show how you can use a simple callback function in order to update the objects on the screen.  In the previous tutorial, we created a scene with one cube and a camera.  In this tutorial we will create a line of cubes.  Each of these cubes will be set spinning in turn.  You can use the same html page from tutorial #2 to show this demo.

/*This demo creates 4 boxes in a row. The left most box will
  start spinning immediately.  The next box will spin 5 sec after
  the page is loaded, the next one 5 sec after that etc.*/

var cam;
var totaltime;
var boxes=new Array();
var isspinning=new Array();

/*this callback function is used by the scene class.  Every time
  the scene is updated, it will get called.  This function tests
  the amount of time elapsed since the page was loaded and
  start a new cube spinning every 5 sec.*/
function spincubes(time){
 //totaltime stores amount of time passed since page was loaded
 //time is in millisecond.  Thus 5000 millisecond is 5 seconds.
 totaltime=totaltime+time;

 //once the 4th cube is spinning it is no longer necessary to check
 if(isspinning[3]==false){
   for(var i=0;i<4;i++){
     if(isspinning[i]==false && totaltime > i*5000 && totaltime < 5000*(i+1)){
       isspinning[i]=true;
       boxes[i].setAngularVel(new Array(Math.random()*0.001,
                      Math.random()*0.001,Math.random()*0.001));
     }
   }
 }
}

//the function that will be called by the web page canvasName is the name
//of the canvas where the scene will show.
function canvasMain(canvasName){
  //create a new Scene object
  var scn = new Scene();
  totaltime=0;
  //check that it was successful
  if(scn.createScene(canvasName)){
    for(var i=0;i<4;i++){
      //create a cube.  by default, this cube is centred at 0,0,0
      boxes[i]=new Cube();
      boxes[i].setPosition(new Array(-4.5+i*3,0,-20));
      //Add the object to the scene
      scn.addObjectToScene(boxes[i]);
      //the box is not currently spinning
      isspinning[i]=false;
    }
    //create a camera
    cam = new FreeCamera();

    //set the camera position
    cam.setPosition(new Array(0,0,0));
    // make it look into the scene (remember +ve z in a right handed system is
    //pointing out of screen, so -ve z is pointing in
    cam.setLookAtPoint(new Array(0,0,-10));
    //add the camera to the scene
    scn.addCameraToScene(cam);
    //add the callback function
    scn.setUpdateCallback(spincubes);
    //start the scene
    scn.startScene();
  }
}