Collision in games - New Graphics Extension Feature

[IonSwitz]

Following a question on the Starling Forum, I realized that this Graphics Extension, with the new Collision stuff can be used in games to great effect.

I have added a method to Stroke called "fromBounds" that creates a bounding box in a Stroke, which can be used for quick collision detection.

The example below creates a "laser" beam that zigzags across the screen. As squares move across , they get hit by the laser beam, but with really quick and fast object aligned and geometry based collision detection.

Why is this awesome? Well, in a game, the developer can create these Strokes to perform the collision detection, addChild them to the stage, and set them to visible = false, and still rely on them for collisions.

The discussion at Starling Forum is here:

http://forum.starling-framework.org/topic/bounds-intersect-question

Another beauty of this? We don't have to generate the triangles to use this, all that is needed is the vertex lines created by addVertex.

The code example follows

[IonSwitz]

package { import flash.display.Shape; import starling.display.graphics.Graphic; import starling.display.graphics.NGon; import flash.geom.Point; import flash.geom.Rectangle; import starling.core.Starling; import starling.display.graphics.Stroke; import starling.display.Sprite; import starling.events.Event;

public class GeometryHitTest extends Sprite
{
    private var hitPoint:Point = new Point();
    private var hitPointVector:Vector.<Point>;
    private var laserStroke: Stroke;
    private var creepStrokes: Vector.<Stroke> = new Vector.<Stroke>();
    private var creepSpeed: Vector.<Number> = new Vector.<Number>();

    public function GeometryHitTest()
    {
        addEventListener(Event.ADDED_TO_STAGE, onAdded);
    }

    private function onAdded ( e:Event ):void
    {
        stage.color = 0;

        laserStroke = new Stroke();
        laserStroke.addVertex(0, 0, 1, 0xFF0000);
        laserStroke.addVertex(300, 200, 1, 0xFF0000);
        laserStroke.addVertex(200, 400, 1, 0xFF0000);
        laserStroke.addVertex(600, 800, 1, 0xFF0000);
        laserStroke.x = 100;
        laserStroke.y = 100;
        addChild(laserStroke);
        laserStroke.visible = true; // set to false when running the actual game

        var i:int = 0;
        var creepBox:Rectangle = new Rectangle(30, 30, 50, 50); // Get this bounding box from your "real" creeps
        for ( i = 0; i < 100; i++ )
        {
            var creepStroke:Stroke = new Stroke();
            creepStroke.fromBounds(creepBox);
            creepStroke.alignPivot();
            creepStroke.x = ((i/10* 60)) ;
            creepStroke.y = ((i%10)*60) + 160;
            addChild(creepStroke);
            creepStroke.visible = true; // set to false when running the actual game
            creepStrokes.push(creepStroke);

            creepSpeed.push(2); // start speed in x for example
        }

        hitPointVector = new Vector.<Point>(100, true);
        for ( i = 0; i < 100; i++ )
            hitPointVector[i] = new Point();

        addEventListener(Event.ENTER_FRAME, enterFrameHandler);
    }

    private function enterFrameHandler( event:Event ):void
    {
        var i:int = 0;
        // Move objects
        for ( i = 0; i < creepStrokes.length; i++ )
        {
            if ( creepStrokes[i].x < 0 || creepStrokes[i].x > 1000)
                creepSpeed[i] = creepSpeed[i] * -1;

            creepStrokes[i].x += creepSpeed[i];
        }
        // perfrom collisions
        for ( i = 0; i < creepStrokes.length; i++ )
        {
            if ( Stroke.strokeCollideTest(laserStroke, creepStrokes[i], hitPoint, hitPointVector) )
            { // hitPoint is one of all hits, use hitPointVector if you want to find all hits.
                creepStrokes[i].rotation += 0.2;
            }
        }
    }

    private function disposeGraphic(g:Graphic) : void
    {
        removeChild(g);
        g.dispose();
    }

}

}

[makc]

I have added a method to Stroke called "fromBounds" that creates a bounding box in a Stroke

why is this not pull request?

[IonSwitz]

Should it be?

I'm not super-great at how GitHub projects usually run, but what would be the benefit of a pull request, when it is completely new functionality?