AS3 Collision Detection - Jumping pushes character through floor

Question

Wellp, I've looked everywhere, and I'm as green as they come at this..

I've recently started playing with AS3 because I want to learn it, so I began building a simple platformer deal.

I think I know what my problem is, but finding the solution has been hades and a half.

From what I can research, this is a matter of player position calculation/framerates. The character has gone too far before the program calculates his position as in relation to the floor, and when it finally recognizes where he is, it begins recalibrating, bringing him back to Zero.

My particular problem is that everyone who makes tutorials and stuff uses different labeling systems and I can't find anything well enough adapted to this particular problem in plainspeak.

So please forgive me for asking, but is there any chance someone could check out my code and help me spot where things are going wrong. I feel like it has something to do with the

if(downBumping) bit, but I'm struggling to figure out what to change and how. :\

Here's the code:

import flash.geom.Point;
import flash.events.KeyboardEvent;
import flash.events.Event;

stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownHandler);
stage.addEventListener(KeyboardEvent.KEY_UP, keyUpHandler);
stage.addEventListener(Event.ENTER_FRAME, loop);

var scrollX:Number = 0;
var scrollY:Number = 0;

var xSpeed:Number = 0;
var ySpeed:Number = 0;

var leftPressed:Boolean = false;
var rightPressed:Boolean = false;
var upPressed:Boolean = false;
var downPressed:Boolean = false;

var leftBumping:Boolean = false;
var rightBumping:Boolean = false;
var upBumping:Boolean = false;
var downBumping:Boolean = false; 

var leftBumpPoint:Point = new Point(-62, 40);
var rightBumpPoint:Point = new Point(62, 40);
var upBumpPoint:Point = new Point(0, -83);
var downBumpPoint:Point = new Point(0, 80);

var animationState:String = "idle";

class Player extends player {
    var speedConstant:int = 4;
    var friction:Number = .75;
    var maxSpeedConstant:Number = 18;
    var gravityConstant:Number = 16;
    var jumpConstant:Number = -180;
}

function loop(e:Event):void{

    if(back.collisions.hitTestPoint(player.x + leftBumpPoint.x, player.y +     leftBumpPoint.y, true)){
        trace("my butt!!");
    leftBumping = true;
    } else {
        leftBumping = false;
    }

    if(back.collisions.hitTestPoint(player.x + rightBumpPoint.x, player.y +     rightBumpPoint.y, true)){
        trace("my face!!");
        rightBumping = true;
    } else {
        rightBumping = false;
    }

    if(back.collisions.hitTestPoint(player.x + upBumpPoint.x, player.y + upBumpPoint.y,     true)){
        trace("my head!!");
        upBumping = true;
    } else {
        upBumping = false;
    }

    if(back.collisions.hitTestPoint(player.x + downBumpPoint.x, player.y +     downBumpPoint.y, true)){
        trace("my feet!");
        downBumping = true;
    } else {
        downBumping = false;
    }

    //speed mechanics
    if(leftPressed){
        xSpeed -= speedConstant;
        player.scaleX = -1;
    } else if(rightPressed){
        xSpeed += speedConstant;
        player.scaleX = 1;
    }   

    if(leftBumping){
        if(xSpeed < 0){
            xSpeed *= -0.5;
        }
    }
    if(rightBumping){
        if(xSpeed > 0){
            xSpeed *= -0.5;
        }
    }
    if(upBumping){
        if(ySpeed < 0){
            ySpeed *= -0.5;
        }
    }
    if(downBumping){
        if(ySpeed > 0){
            ySpeed *= -.19;
        }
        if(upPressed){ //and if we're pressing UP
            ySpeed = jumpConstant; //set y speed to jump constant
        }
    } else {//if we are not touching the floor
        ySpeed += gravityConstant; //accelerate downwards       
    }   

    if(xSpeed > maxSpeedConstant){
        xSpeed = maxSpeedConstant;
    } else if(xSpeed < (maxSpeedConstant * -1)){
        xSpeed = (maxSpeedConstant * -1);
    }

    xSpeed *= friction;
    ySpeed *= friction;

    if(Math.abs(xSpeed) < 0.5){
        xSpeed = 0;
    }

    scrollX -= xSpeed;
    scrollY -= ySpeed;

    back.x = scrollX;
    back.y = scrollY;

    if( ( leftPressed || rightPressed || xSpeed > speedConstant || xSpeed <     speedConstant *-1) && downBumping){
        animationState = "walk";
    }else if(downBumping){
        animationState = "idle";
    }

    if(player.currentLabel !=animationState){
        player.gotoAndStop(animationState)
    }
}


function keyDownHandler(e:KeyboardEvent):void{
    if(e.keyCode == Keyboard.LEFT){
        leftPressed = true;
    } else if(e.keyCode == Keyboard.RIGHT){
        rightPressed = true;
    } else if(e.keyCode == Keyboard.UP){
        upPressed = true;
    } else if(e.keyCode == Keyboard.DOWN){
        downPressed = true;
    }
}

function keyUpHandler(e:KeyboardEvent):void{
    if(e.keyCode == Keyboard.LEFT){
        leftPressed = false;
    } else if(e.keyCode == Keyboard.RIGHT){
        rightPressed = false;
    } else if(e.keyCode == Keyboard.UP){
        upPressed = false;
    } else if(e.keyCode == Keyboard.DOWN){
        downPressed = false;
    }
}

Any help would be so very appreciated. I want to learn, but it's hard when I don't even know what exactly to look for.. Thanks so much!

score 0 · Answer 1 · answered Feb 19 '14 at 07:18

I'm going to write you what you need to change for a little solution. But that's not the best effort. I just don't wanted to change your whole logic, but you can use this in your logic.

don't use a time based calculation for fixing y position after a jump, let that calculation be instant

if your player's y position get's below of zero point, set it's y position to zero and stop accelerating down

Also, an important point, don't use your hittest functions first, use them after your acceleration functions, in every loop, that makes better effort.

Also, increasing framerate of your movie and decreasing acceleration values is great way to make things work so much better.

AS3 Collision Detection - Jumping pushes character through floor

1 Answers1