LibGDX - restrict zooming of perspective camera

Question

What is the best way to restrict zooming of perspective camera in LibGDX? I have a planet in space and I need to zoom in/out it. Zooming works great, but I have to limit it to prevent the planet to be so close to the user and far away from him. Now, I'm using standart CameraInputController to zoom in/out and restrict it by using the following code:

protected boolean pinchZoom (float amount) {
    if(rho>25.f && rho<60.f){           
        return zoom(pinchZoomFactor * amount);
    }

    camera.update();
    rho = calculateRho();

    if(rho<=25.0){          
        while(rho<=25.0){
            zoom(-.1f);
            camera.update();
            rho = calculateRho();
        }           
    }

    if(rho>=60){            
        while(rho>=60.0){
            zoom(.1f);
            camera.update();
            rho = calculateRho();
        }           
    }
}

private float calculateRho(){
         return (float) Math.sqrt(Math.pow(camera.position.x, 2)+
                Math.pow(camera.position.y, 2)+Math.pow(camera.position.z, 2)); 
}

Using this code my camera shakes sometimes a little bit. So, I find another way.

Answer 1

I've found the solution. I just declare variable which sums input variable amount and then I check range of this value.

float currentZoom=0;
private final float maxZoom = .5f;
private final float minZoom = -2.1f;

protected boolean pinchZoom (float amount) {
    currentZoom += amount;      
    if(currentZoom>=maxZoom) currentZoom=maxZoom;
    if(currentZoom<=minZoom) currentZoom=minZoom;

    if(currentZoom>minZoom && currentZoom<maxZoom){
        return zoom(pinchZoomFactor * amount);
    }
    return false;
}

It works perfect for me! I hope this solution helps someone else.