The collision in SFML is not that good, how to improve it? - c++

Question

I've been lately working on a simple game using C++ and SFML latest version, but I had a problem which is that the collision detection is not that good, for example the player dies even if the enemy didn't touch him yet, but just near him. Here is the code of the player class with the move function and collision detection code AND the moves of the enemy class:
`class PlayerA : public CircleShape
{
public:
//Constructor:
PlayerA(float xposition, float yposition, float radius, float s)
{
setRadius(radius);
setFillColor(Color::Yellow);
setOutlineColor(Color(00,80,00));
setOutlineThickness(-2);
setPointCount(3);
setSpeed(s);
setPosition(xposition,yposition);
}
//Movements of the player:
void up()
{
move(0,-10*speed);
}
void down()
{
move(0,10*speed);
}
void right()
{
move(10*speed,0);
}
void left()
{
move(-10*speed,0);
}
void checkA(ObsA *obs1=NULL,ObsA *obs2=NULL, ObsA *obs3=NULL, ObsA *obs4=NULL, ObsA *obs5=NULL)
{
if(obs2==NULL)
{
if(getGlobalBounds().intersects(obs1->getGlobalBounds()))
{
relevel();
}
}
private:
float speed=0.00;
void obs()
{
if(speed > 0)
{
rotate(0.5*speed);
}
else
{
rotate(0.5*speed);
}
}
private:
float speed = 0.00;
void obs()
{
if(speed > 0)
{
rotate(0.5*speed);
}
else
{
rotate(0.5*speed);
}
}
private:
float speed = 0.00;
Is there something wrong with the code, how to fix the problem, thank you!

Answer 1

The intersects function just check if two rectangles intersect. If you want pixel perfect collision detection in SFML you have to write that yourself.
Basically, start with intersects, if it is true, then get the intersecting rectangle and check if any pixels therein from both original rectangles contains overlaping relevant pixels.

Answer 2

You can use this function to perform better collision detection.Its a basic one but works well
bool circleTest(const sf::Sprite &first, const sf::Sprite &second)
{
sf::Vector2f firstRect(first.getTextureRect().width, first.getTextureRect().height);
firstRect.x *= first.getScale().x;
firstRect.y *= first.getScale().y;
sf::Vector2f secondRect(second.getTextureRect().width, second.getTextureRect().height);
secondRect.x *= second.getScale().x;
secondRect.y *= second.getScale().y;
float r1 = (firstRect.x + firstRect.y) / 4;
float r2 = (secondRect.x + secondRect.y) / 4;
float xd = first.getPosition().x - second.getPosition().x;
float yd = first.getPosition().y - second.getPosition().y;
return std::sqrt(xd * xd + yd * yd) <= r1 + r2;
}

Answer 3

Are you using a circle? If I remember correctly, the circle will have a rectangle hitbox. If that is the case, then you may have collision between the invisible rectangle corners.
If you're using a circle, Perhaps change class to a square rectangle and see if collision works correctly. Or try testing collision directly on an x or y axis with your circles; i.e. having them moving in a straight line towards each other only changing 1 axis. (the edge of the circle will be the same as the edge of the rectangle at the left, right, top, and bottom sections).
If you're needing a better collision for circles, there may be one already built in SFML. But I don't think it would be too much to write your own logic using the radius of your two circles, the center of your two objects, and the angle hypotenuse between the centers.
edit based on Merlyn Morgan-Graham's comment.