BrightnessGUI.js

var lightSource : GameObject;
var brightnessGuiTrigger : GameObject;
var minIntensity : float;
var maxIntensity : float;
var lightIntensity : float;

private var brightnessSliderOpen = false;

function Start () {
  Hide();
}

function Update () {
  if (Input.touchCount == 1 && Input.GetTouch(0).tapCount == 2) {
    var touch = Input.GetTouch(0);
    var ray = Camera.main.ScreenPointToRay(touch.position);
    var hit : RaycastHit;
    
    if (Physics.Raycast(ray, hit)) {
      if (hit.collider.gameObject == brightnessGuiTrigger) {
        if (brightnessSliderOpen) {
          Hide();
        }
        else {
          Show();
        }
      }
    }
  }
  
  lightSource.light.intensity = lightIntensity;
  
  var dark = Color(87, 77, 71, 1);
  var light = Color(248, 231, 212, 1);
  var percentOfFullIntensity = 1 - (((maxIntensity - minIntensity) - (lightIntensity - minIntensity)) / (maxIntensity - minIntensity));
  Debug.Log(Color.Lerp(dark, light, percentOfFullIntensity));
  RenderSettings.ambientLight = Color(87, 77, 71, 1);
}

function OnGUI () {
  if (brightnessSliderOpen) {
    GUI.Label(Rect((Screen.width / 2) - 32, 10, 100, 30), "Brightness");
    lightIntensity = GUI.HorizontalSlider(Rect((Screen.width / 2) - 50, 35, 100, 30), lightIntensity, minIntensity, maxIntensity);
  }
  
}

function Hide () {
  brightnessSliderOpen = false;
}

function Show () {
  brightnessSliderOpen = true;
}