Detecting right/left collisions with a bounding box

Question

I'm building a platformer in cocos2d, my first game project. I'm working on movement and collision detection. I'm using a tilemap with a "meta" layer of invisible blocks that are designated collidable.

Everything seems to work pretty well except for one minor detail: when the character jumps from above into a platform, he does not fall but clips through it. If he jumps from below, it recognizes it and resets his Y velocity accordingly. I know that it's because of how I'm detecting the collisions, and just doing a simple comparison of the origin.y's, but I'm unsure of how to refactor this code better:

- (void) update: (ccTime) dt {
    CGPoint scaledVelocity = ccpMult(leftJoystick.velocity, 35.0f);
    CGPoint newPosition = ccp(player.position.x + scaledVelocity.x * dt, player.position.y);
    CGPoint oldPosition = [player position];

    float velocityX = player.Velocity.x + scaledVelocity.x * dt;
    float velocityY = player.Velocity.y;

    BOOL isCollision = NO;
    BOOL isCollisionBelow = NO;
    BOOL isCollisionRight = NO;
    BOOL isCollisionLeft = NO;

    NSMutableArray* collisionSprites = [[NSMutableArray alloc] init];

    if (oldPosition.x > newPosition.x) {
        player.flipX = YES;
    }
    else if (oldPosition.x < newPosition.x) {
        player.flipX = NO;
    }

    for (CCSprite* sprite in gameplayLayer.collidableTiles) {
        if (CGRectIntersectsRect(player.boundingBox, sprite.boundingBox)) {
            isCollision = YES;
            [collisionSprites addObject:sprite];
        }
    }

    // Figure out which direction collision is in
    if (isCollision) {
        for (CCSprite* collisionSprite in collisionSprites) {
            if (collisionSprite.boundingBox.origin.y < player.boundingBox.origin.y) {
                isCollisionBelow = YES;
            }
            if ((collisionSprite.boundingBox.origin.x > player.boundingBox.origin.x) && (collisionSprite.boundingBox.origin.y >= player.boundingBox.origin.y)) {
                isCollisionRight = YES;
            }
            if ((collisionSprite.boundingBox.origin.x < player.boundingBox.origin.x) && (collisionSprite.boundingBox.origin.y >= player.boundingBox.origin.y)) {
                isCollisionLeft = YES;
            }
        }
    }

    if (isCollisionLeft) {
        velocityX = 0.5f;
    }
    else if (isCollisionRight) {
        velocityX = -0.5f;
    }

    if (isCollision && !isCollisionBelow && player.characterState != kStateFalling) {
        velocityY = 0;
        velocityY -= 0.8f;
        [player setCharacterState:kStateFalling];
    }
    else if (!isCollisionBelow) {
        velocityY -= 0.7f;
    }
    else if (isCollisionBelow) {
        velocityY = 0;
        [player setCharacterState:kStateIdle];
    }

    if (rightButton.active) {            
        if (player.characterState != kStateJumping) {
            velocityY += 15.0f;
            [player setCharacterState:kStateJumping];
        }
    }

    // Ground friction
    if (player.Velocity.x > 0) {
        if (player.Velocity.x < 0.5f) {
            velocityX = 0;
        }
        else {
            velocityX -= 0.5f;
        }
    }

    if (player.Velocity.x < 0) {
        velocityX += 0.5f;
    }

    [player setVelocity:ccp(velocityX, velocityY)];
    [player setPosition: ccp(player.position.x + player.Velocity.x, player.position.y + player.Velocity.y)];
    [gameplayLayer setViewpointCenter:newPosition];
    [player setOldPosition: player.position];
}

How can I refactor this code to work properly from all angles and reduce the complexity (I feel that there's too many booleans, and they all get a bit confusing).

Answer 1

As far as I know the Boundingbox rect has two properties origin and size. to check if some obejct is colliding from any of the sides you have to check both values: so I suggest you change your code like following :

if (CGRectMaxY(collisionSprite.boundingBox) < CGRectMinY(player.boundingBox)) {
    isCollisionBelow = YES;
}
if (CGRectMaxX(collisionSprite.boundingBox) < CGRectMinX(player.boundingBox)) {
    isCollisionRight = YES;
}
if (CGRectMinX(collisionSprite.boundingBox) > CGRectMaxX(player.boundingBox)) {
    isCollisionLeft = YES;
}