zooming out in webgl

I saw here Click to zoom in WebGL how to zoom in to a particular point. How can I reverse that functionality- i.e. 开发者_如何学Pythonzoom out?

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Change the statement

  vec3.subtract(eye,dir) ;

to

  vec3.add(eye,dir) ;

This moves the eye in the opposite direction from before.

Here's the modified live example: http://jsfiddle.net/3wwdU/1/