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;
}
bool Bullet::detectCollision(sf::Vector2f p, const sf::Sprite& sprite) const
{
/* collide if the pixel is not transparent */
int img_width = sprite.GetSize().x, img_height = sprite.GetSize().y;
int img_x = pos.x - p.x + img_width / 2, img_y = pos.y - p.y + img_height / 2;
if (img_x < 0 || img_x >= img_width)
return false;
if (img_y < 0 || img_y >= img_height)
return false;
return sprite.GetPixel(img_x, img_y).a != 0;
}
/*!
* \brief Tests whether the sprite Obj1 collides with the sprite Obj2
* \param Obj1 The first of the two objects
* \param Obj2 The second of the two objects
* \param AlphaLimit The limit of the alpha value
* \return Are the two objects are in collision (via a pixel-perfect method) ?
*
* It tests using a pixel-perfect condition, with AlphaLimit to test whether
* the pixels are colliding.
*/
bool Collision::PixelTest(const sf::Sprite &Obj1, const sf::Sprite &Obj2,
sf::Uint8 AlphaLimit)
{
sf::IntRect Obj1BoundingBox(GetBoundingBox(Obj1));
sf::IntRect Obj2BoundingBox(GetBoundingBox(Obj2));
sf::IntRect Intersection;
if (!Obj1BoundingBox.Intersects(Obj2BoundingBox, &Intersection))
return false;
if (AlphaLimit == 0)
return true;
for (int I = Intersection.Left ; I <= Intersection.Right ; ++I)
{
for (int J = Intersection.Top ; J <= Intersection.Bottom ; ++J)
{
sf::Vector2i Obj1Pix(I - Obj1BoundingBox.Left, J
- Obj1BoundingBox.Top);
sf::Vector2i Obj2Pix(I - Obj2BoundingBox.Left, J
- Obj2BoundingBox.Top);
if (Obj1Pix.x >= 0 && Obj1Pix.x < Obj1BoundingBox.GetWidth()
&& Obj1Pix.y >= 0 && Obj1Pix.y
< Obj1BoundingBox.GetHeight() && Obj2Pix.x >= 0
&& Obj2Pix.x < Obj2BoundingBox.GetWidth() && Obj2Pix.y >= 0
&& Obj2Pix.y < Obj2BoundingBox.GetHeight()
&& Obj1.GetPixel(Obj1Pix.x, Obj1Pix.y).a > AlphaLimit
&& Obj2.GetPixel(Obj2Pix.x, Obj2Pix.y).a > AlphaLimit)
return true;
}
}
return false;
}
