collision as3 dectect - actionscript-3

Question

hi im trying to make a basic game on adobe flash as3 to help learn collision dection, the aim is to make your way through traffic. the player (box_MC) has to make it to the other side and the other objects are in the way (cycle) which have collision detection. i did the collision detection by going into cycle movieclip and making other smaller cycles which if you hit creates collision.
the collision error lies with if the player moves down onto the cycle it doesnt run the collision
p.s if there is a better way of doing the collision how is it done?

Answer 1

hitTestObject() and hitTestPoint() aren't very good when it comes to collision detection, which is somewhat ironic since, of course, those are the first things most people look at when trying to implement collisions. However, I've found that simple math (like, really simple) combined with an equally simple while() loop is the best way to go about it.
What I do is:
// the stage collision box
var mStageRect:Rectangle = new Rectangle(/*stage collision box properties here*/);
// create a Point object that holds the location of the bottom center of the player
var mPlayerBase:Point = new Point(player.x + (player.width / 2), player.y + player.height);
// call this function every frame through your game loop (onEnterFrame)
private function checkCollision(e:Event):void
{
// while the player's bottom center point is inside of the stage...
while (rectContainsPoint(mStageRect, mPlayerBase))
{
// decrement the player's y
player.y--;
// set gravity to 0
player.gravity = 0;
// set isOnGround to true
player.isOnGround = true;
}
}
// checks if a point is currently positioned within the bounds of a rectangle object using ultra simple math
private function rectContainsPoint(rect:Rectangle, point:Point):Boolean
{
return point.x > rect.x && point.x < rect.x + rect.width && point.y > rect.y && point.y < rect.y + rect.height;
}
This is waaaaaaay more efficient than hitTestObject/Point, imo, and has given me no problems.