JavaFX, Side Scrolling Gaming

I started to make several small JavaFX game demos. I’m doing that to fell where JavaFX is good to make this sort of game and what patterns would be frequently needed to implement, where I will place a little framework for fast development of simple casual games. What I’m calling now just ‘GameFX’. My first experiment was to creating a side scrolling animation that’s is usefull to create the parallax effect in side scrolling games. For that I created the class Slidding. You create an Slidding with a set of nodes and they will slide from right to left and when a node reaches the left side it back to the right side.

Example:

Slidding {
    content: [
       Circle {
           centerX: 100, centerY: 100, radius: 40
           fill: Color.RED
       },
       Circle {
           centerX: 300, centerY: 100, radius: 40
           fill: Color.BLUE
       }
    ]
    clock: 0.05s
 }

That produces:

You create a Slidding with a list of Nodes at content, a clock (that will determine the speed of that animation) and a width. If you don’t provide a width, the slidding will do the best effort to determine one. You can use this approach to create more complex scenarios, using more Slidding groups.

This is a example of that:

import javafx.application.*;
import javafx.animation.*;
import javafx.scene.geometry.*;
import javafx.scene.paint.*;
import javafx.scene.*;

import gamefx.Slidding;

var SCREENW = 500;
var SCREENH = 400;

/* the sky is a light blue rectangle */
var sky = Rectangle {
    width: SCREENW, height: SCREENH
    fill: LinearGradient {
        startX: 0.0 , startY: 0.0
        endX: 0.0, endY: 1.0
        proportional: true
        stops: [
            Stop { offset: 0.0 color: Color.LIGHTBLUE },
            Stop { offset: 0.7 color: Color.LIGHTYELLOW },
            Stop { offset: 1.0 color: Color.YELLOW }
        ]
    }
}

/* the ground is a olive rectangle */
var ground = Rectangle {
    translateY: 300
    width: 500, height: 100
    fill: LinearGradient {
        startX: 0.0 , startY: 0.0
        endX: 0.0, endY: 1.0
        proportional: true
        stops: [
            Stop { offset: 0.2 color: Color.OLIVE },
            Stop { offset: 1.0 color: Color.DARKOLIVEGREEN }
        ]
    }
}

/* a clod cloud is like an ellipse */
class Cloud extends Ellipse {
    override attribute radiusX = 50;
    override attribute radiusY = 25;
    override attribute fill = Color.WHITESMOKE;
    override attribute opacity = 0.5;
}

/* we create a slidding of clouds */
var clouds = Slidding {
    content: [
        Cloud{centerX: 100, centerY: 100},
        Cloud{centerX: 150, centerY:  20},
        Cloud{centerX: 220, centerY: 150},
        Cloud{centerX: 260, centerY: 200},
        Cloud{centerX: 310, centerY:  40},
        Cloud{centerX: 390, centerY: 150},
        Cloud{centerX: 450, centerY:  30},
        Cloud{centerX: 550, centerY: 100},
    ]
    clock: 0.2s
}

var SUNX = 100;
var SUNY = 300;
var rotation = 0;

/* the sun, with it's corona */
var sun = Group {
    rotate: bind rotation
    anchorX: SUNX, anchorY: SUNY
    content: [
        for (i in [0..11]) {
            Arc {
                centerX: SUNX, centerY: SUNY
                radiusX: 500, radiusY: 500
                startAngle: 2 * i * (360 / 24), length: 360 / 24
                type: ArcType.ROUND
                fill: Color.YELLOW
                opacity: 0.3
            }
        },
        Circle {
            centerX: SUNX, centerY: SUNY, radius: 60
            fill: Color.YELLOW
        },
    ]
}

/* animate the corona changing the it rotation angle */
var anim = Timeline {
    repeatCount: Timeline.INDEFINITE
    keyFrames : [
        KeyFrame {
            time : 0s
            values: rotation => 0.0 tween Interpolator.LINEAR
        },
        KeyFrame {
            time : 2s
            values: rotation => (360.0/12) tween Interpolator.LINEAR
        },
    ]
}
anim.start();

/* a tree is a simple polygon */
class Tree extends Polygon{
    public attribute x = 0;
    public attribute y = 0;
    override attribute points = [0,0, 10,30, -10,30];
    override attribute fill = Color.DARKOLIVEGREEN;
    init{
        translateX = x;
        translateY = y;
    }
}

/* a forest is a lot of trees */
var forest = Slidding{
    content: [
        Tree{x: 20, y: 320}, Tree{x: 80, y: 280}, Tree{x:120, y: 330},
        Tree{x:140, y: 280}, Tree{x:180, y: 310}, Tree{x:220, y: 320},
        Tree{x:260, y: 280}, Tree{x:280, y: 320}, Tree{x:300, y: 300},
        Tree{x:400, y: 320}, Tree{x:500, y: 280}, Tree{x:500, y: 320}
    ]
    clock: 0.1s
    width: SCREENW
}

Frame {
    title: "Side Scrolling"
    width: SCREENW
    height: SCREENH
    closeAction: function() {
        java.lang.System.exit( 0 );
    }
    visible: true

    stage: Stage {
        content: [sky, sun, clouds, ground, forest]
    }
}

Producing:

If you want to try these examples, place this Slidding implementation as Slidding.fx in a directory named gamefx, or grab here the NetBeans project.

package gamefx;

import javafx.scene.CustomNode;
import javafx.scene.Node;
import javafx.scene.Group;
import javafx.animation.Timeline;
import javafx.animation.KeyFrame;

/*
 * The slidding group of nodes for side scrolling animations.
 *
 * @example
 * Slidding {
 *    width: 300
 *    content: [
 *       Circle { centerX: 100, centerY: 100, radius: 40, fill: Color.RED },
 *       Circle { centerX: 200, centerY: 100, radius: 40, fill: Color.BLUE },
 *    ]
 *    clock: 0.05s
 * }
 */
public class Slidding extends CustomNode {
    public attribute content: Node[];
    public attribute clock = 0.1s;
    public attribute width: Number;

    public attribute autostart = true;
    public attribute cycle = true;

    public attribute anim = Timeline {
        repeatCount: Timeline.INDEFINITE
        keyFrames : [
            KeyFrame {
                time : clock
                action: function() {
                    for(node in content){
                        node.translateX--;
                        if (node.getX() + node.translateX + node.getWidth() <= 0){
                            if(cycle){
                                node.translateX = width - node.getX();
                            } else {
                                delete node from content;
                            }
                        }
                    }
                } // action
            } // keyframe
        ]
    } // timeline 

    public function create(): Node {
        // if width is not setted, we try to figure out
        if(width == 0) {
            for(node in content) {
                if(node.getX() + node.getWidth() > width) {
                    width = node.getX() + node.getWidth();
                }
            }
        }

        // normaly the slidding will start automaticaly
        if(autostart){
            anim.start();
        }

        // just a Group of Nodes
        return Group {
            content: content
        };
    }
}

Is not the final implementation but it’s a idea. Soon I’ll show a demo game I did using theses codes.