code: public void setAmbientLight(float r, float g, float b, float a) {
  		this.ambientLight.set(r, g, b, a);
  	}
docs: Sets ambient light color.
  Specifies how shadows colored and their brightness.
  
  <p>Default = Color(0, 0, 0, 0)
  
  @param r
  shadows color red component
  @param g
  shadows color green component
  @param b
  shadows color blue component
  @param a
  shadows brightness component
  
  @see #setAmbientLight(float)
  @see #setAmbientLight(Color)