Camera and User Interaction - WebGL Game Development - page 192

Using an orbit camera
Open 05-Loading-Scene-OrbitCamera.html in your favorite text editor. The only
change we have in this file is to replace the free camera object with the orbit camera
object. Also, set the basic properties for the orbit camera.
cam=new OrbitCamera();
cam.setFarthestDistance(300);
cam.setClosestDistance(60);
cam.setOrbitPoint([0.0, 20.0, 0.0]);
cam.setDistance(100);
We added some changes to primitive/KeyboardInteractor.js to handle the
orbit camera.
If the camera object is of the OrbitCamera type, then only two keys are functional,
the up and down arrow keys. We invoke the goCloser and goFarther functions of
the camera object.
if(this.cam instanceof OrbitCamera) {
switch(event.keyCode) {//determine the key pressed
case 65://a key
case 37://left arrow
break;
case 68://d key
case 39://right arrow
break;
case 83://s key
break;
case 40://down arrow
this.cam.goFarther(10);//move + on the Z axis
break;
case 38://up arrow
this.cam.goCloser(10);//move - along the Y axis (down)
break;
}
}
The changes in primitive/MouseInteractor.js are listed as follows:
MouseInteractor.prototype.translate = function(value) {
...
if(c instanceof OrbitCamera) {
if(dv>0) {
c.goFarther(dv);
}