Apparently RadialGradient has issue computing the proper radii when applied to non square/circular surface.

The gradient rendered on screen is not what it is supposed to be. Take the following example:

public class Test extends Application {

    @Override
    public void start(Stage primaryStage) {
        final Rectangle rectangle = new Rectangle(100, 100, 150, 100);
        rectangle.setFill(new RadialGradient(0, 0, 0.5, 0.5, 1, true, CycleMethod.NO_CYCLE, new Stop(0, Color.RED), new Stop(0.5, Color.GREEN), new Stop(1, Color.BLUE)));
        final Pane root = new Pane();
        root.getChildren().add(rectangle);
        final Scene scene = new Scene(root, 600, 600);
        primaryStage.setTitle("Test");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }
}

As of u_20 and under Windows, the blue color is barely present on screen. In fact, the green color which is set to be at the middle of the gradient overpasses all 4 borders of the rectangle on both the X and Y axis. It should not do that.

Now take a look at http://www.w3schools.com/css/tryit.asp?filename=trycss3_gradient-radial where a similar gradient is rendered in HTML (requires IE version > 9).

Here, the blue color sits on the very edge of the rectangle on the X and Y axis. The blue color is fully visible within the 4 corners (as those areas are beyond the radii of the ellipse).
This is how the JavaFX radial gradient should be rendered. Currently it is not.