Collision Detection Problem

[MrBob1337]

I wrote a small chunk of code for my SFML game that (should) cycle through every entity and check if it collides with the given entity. If it finds a match, it returns the entity (pointer) and breaks from the loop.

However, this is not what happens. It ALWAYS returns a value, even if it's far away from any other entity. Here is the code:

TwoDEntity * GameManager::IsCollidingAny(TwoDEntity * ent,sf::Uint8 AlphaLimit)
{
	int i;
	for(i = 0; i < ulist.size(); i++)
	{
			
		
		if(ulist.at(i)->GetCanCollide())
		{
			TwoDEntity * check = dynamic_cast<TwoDEntity*>(ulist.at(i)); //uses dynamic_cast to get the key state //ulist.at(i);
			if(IsColliding(ent->GetSprite(),check->GetSprite(),AlphaLimit))
			{
				//return check;
				//return 0;
				return check;
			}
			check = NULL;
			delete check;
		}
		else
		{
			continue;
		}
	}
	return NULL;
}

The algorithim (Some SFML knowledge probably needed):

bool Collision::PixelPerfectTest(const sf::Sprite& Object1, const sf::Sprite& Object2, sf::Uint8 AlphaLimit) 
{
        //Get AABBs of the two sprites
    sf::IntRect Object1AABB = GetAABB(Object1);
    sf::IntRect Object2AABB = GetAABB(Object2);
 
    sf::IntRect Intersection;
 
    if (Object1AABB.Intersects(Object2AABB, &Intersection)) {
 
        //We've got an intersection we need to process the pixels
        //In that Rect.
 
        //Bail out now if AlphaLimit = 0
        if (AlphaLimit == 0) return true;
 
        //There are a few hacks here, sometimes the TransformToLocal returns negative points
        //Or Points outside the image.  We need to check for these as they print to the error console
        //which is slow, and then return black which registers as a hit.
 
        sf::IntRect O1SubRect = Object1.GetSubRect();
        sf::IntRect O2SubRect = Object2.GetSubRect();
 
        sf::Vector2i O1SubRectSize(O1SubRect.GetWidth(), O1SubRect.GetHeight());
        sf::Vector2i O2SubRectSize(O2SubRect.GetWidth(), O2SubRect.GetHeight());
 
        sf::Vector2f o1v;
        sf::Vector2f o2v;
        //Loop through our pixels
        for (int i = Intersection.Left; i < Intersection.Right; i++) {
            for (int j = Intersection.Top; j < Intersection.Bottom; j++) {
 
                o1v = Object1.TransformToLocal(sf::Vector2f(i, j)); //Creating Objects each loop :(
                o2v = Object2.TransformToLocal(sf::Vector2f(i, j));
 
                //Hack to make sure pixels fall withint the Sprite's Image
                if (o1v.x > 0 && o1v.y > 0 && o2v.x > 0 && o2v.y > 0 &&
                        o1v.x < O1SubRectSize.x && o1v.y < O1SubRectSize.y &&
                        o2v.x < O2SubRectSize.x && o2v.y < O2SubRectSize.y) {
 
                    //If both sprites have opaque pixels at the same point we've got a hit
                    if ((Object1.GetPixel(static_cast<int> (o1v.x), static_cast<int> (o1v.y)).a > AlphaLimit) &&
                            (Object2.GetPixel(static_cast<int> (o2v.x), static_cast<int> (o2v.y)).a > AlphaLimit)) {
                        return true;
                    }
                }
            }
        }
        return false;
    }
    return false;
}

Do you see anything that could falsely return a non-NULL value, O great programming gods?

[jA_cOp]

...

You only have one return statement that can return a non-zero value. And it's only reached if IsColliding returns true, which is a function we can't see. We can't help you.

Regardless,
[cpp]
check = NULL;
delete check;
[/cpp]
You might wanna switch those two lines :)

[MrBob1337]

Sorry, I've never been good at Programming posts. IsColliding is just a abstraction of another function, which is the algorithim. I'll post it.

To the best of my knowledge, it returns true if there is a collision and false if there isn't. Pretty simple.