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Pre-Collision Detection question

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Junior Poster in Training
58 posts since Jul 2010
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FYI - I'm coding in actionscript 3.0 but didn't see an area to post for that language.

I made a simple character and a block. I'm trying to get it so that if the character will touch the box, it wont let him move to imply a wall/collision.

I've got him moving but the problem is that it doesn't PREdetect the collision. It lets him overlap the block once, then when I try to move again, it wont go anywhere because NOW (that it's too late), he's overlapping and thus colliding. Anyone know how I can very simply edit this code so the player isn't allowed to overlap the block in the first place?

import flash.display.Sprite;
import flash.events.KeyboardEvent;

var block:Sprite = MovieClip(blockInst);
var player:Sprite = MovieClip(playerInst);
var speed:Number = 10;

stage.addEventListener(KeyboardEvent.KEY_DOWN, playerMovement);

function playerMovement(key:KeyboardEvent):void
	if (player.hitTestObject(block))
		switch (key.keyCode)
			case 37 ://Left
				player.x -=  speed;

			case 39 ://Right
				player.x +=  speed;

			case 38 ://Up
				player.y -=  speed;

			case 40 ://Down
				player.y +=  speed;

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Industrious Poster
4,052 posts since Dec 2008
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Yea so this is a problem of collision response. Once a collision is detected what do you do? Well in this case you should move your player back just before the collision point. So if there is a collision, shift back the player's position so that there is not a collision anymore. Get it?

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