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@PrimaryFeather
Created February 5, 2021 07:12
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Sample (for Starling Framework) showing how to detect collisions between a complex and a simple object.
package starling
{
import flash.geom.Matrix;
import flash.geom.Point;
import starling.display.Canvas;
import starling.display.Sprite;
import starling.events.Touch;
import starling.events.TouchEvent;
import starling.events.TouchPhase;
import starling.geom.Polygon;
import starling.utils.MatrixUtil;
import starling.utils.Pool;
public class CollisionDetectionSample extends Sprite
{
private var _moon:Sprite;
private var _ball:Sprite;
private var _moonPolygon:Polygon;
private const _moonVertices:Array = [
50, 0,
36, 16,
29.6, 32,
27.2, 50,
29.6, 68,
36, 84,
50, 100,
24, 92.7,
7.3, 76,
0, 50,
7.3, 24,
24, 7.3
];
private const _ballVertices:Array = [10, 0, 20, 10, 10, 20, 0, 10];
public function CollisionDetectionSample()
{
_moonPolygon = new Polygon(_moonVertices);
var moonCanvas:Canvas = new Canvas();
moonCanvas.beginFill(0xff0000);
moonCanvas.drawPolygon(_moonPolygon);
moonCanvas.endFill();
_moon = new Sprite();
_moon.addChild(moonCanvas);
_moon.x = 150;
_moon.y = 100;
_moon.scale = 2.0;
_moon.rotation = 0.5;
addChild(_moon);
var ballPolygon:Polygon = new Polygon(_ballVertices);
var ballCanvas:Canvas = new Canvas();
ballCanvas.beginFill(0xff);
ballCanvas.drawPolygon(ballPolygon);
ballCanvas.endFill();
_ball = new Sprite();
_ball.addChild(ballCanvas);
_ball.x = 200;
_ball.y = 250;
_ball.addEventListener(TouchEvent.TOUCH, onBallTouched);
addChild(_ball);
}
public function onBallTouched(event:TouchEvent):void
{
var touch:Touch = event.getTouch(this, TouchPhase.MOVED);
if (touch != null)
{
var movement:Point = event.getTouch(_ball).getMovement(this);
_ball.x += movement.x;
_ball.y += movement.y;
testForCollision();
}
}
private function testForCollision():void
{
var matrix:Matrix = _ball.getTransformationMatrix(_moon);
var numCollidingPoints:int = 0;
for (var i:int = 0; i < _ballVertices.length; i += 2)
{
var ballVertex:Point = Pool.getPoint(_ballVertices[i], _ballVertices[i+1]);
var ballVertexInMoon:Point = MatrixUtil.transformPoint(
matrix, ballVertex, Pool.getPoint());
if (_moonPolygon.containsPoint(ballVertexInMoon))
numCollidingPoints += 1;
Pool.putPoint(ballVertex);
Pool.putPoint(ballVertexInMoon);
}
trace("number of points colliding: " + numCollidingPoints);
}
}
}
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