code: protected RadialGradientPaint createArea3DEffectGradient(final int WIDTH, final float RADIUS_FACTOR) {
          final float[] FRACTIONS;
          final Color[] COLORS;
  
          FRACTIONS = new float[]{
              0.0f,
              0.6f,
              1.0f
          };
          COLORS = new Color[]{
              new Color(1.0f, 1.0f, 1.0f, 0.75f),
              new Color(1.0f, 1.0f, 1.0f, 0.0f),
              new Color(0.0f, 0.0f, 0.0f, 0.3f)
          };
          final Point2D GRADIENT_CENTER = new Point2D.Double(WIDTH / 2.0, WIDTH / 2.0);
  
          return new RadialGradientPaint(GRADIENT_CENTER, WIDTH * RADIUS_FACTOR, FRACTIONS, COLORS);
      }
docs: Returns a radial gradient paint that will be used as overlay for the track or area image
  to achieve some kind of a 3d effect.
  @param WIDTH
  @param RADIUS_FACTOR
  @return a radial gradient paint that will be used as overlay for the track or area image