I've been exploring into [Nim Game](https://en.wikipedia.org/wiki/Nim) on Android. The players are going to take objects from heaps. I use openGLES to draw the objects and heaps. Where I'm stuck is how to "take".   

As the samples shown on [official dev guide](http://developer.android.com/resources/articles/glsurfaceview.html), I can override `onTouchEvent` method in the class that `extends GLSurfaceView` for the interaction. However, how I could tell where the objects have been drawn? Or are there any objects at the coordinates where I touch?  

Any ideas?