Messages

1

General / Implementing "place_empty" function in C++ from GameMaker

« on: May 16, 2021, 11:53:35 am »

Hi, recently I started writing a 2D game in C++ with SFML but now I'm stuck in the collision mechanism. I want to program the entities in a way so that every time Update() is called I check whether they are touching with solid objects and determine how they should move (up/down left/right).

In case you didn't know, in GameMaker (legacy versions) there are two functions, place_empty(x, y) which checks if there is a collision box in the given coordinates and position_empty(x, y) which checks if the calling object interacts with another object in the given coordinates.

bool PositionFree(sf::Vector2f Position, bool Solid) {
    // GetEntities() returns a pointer to this type -> std::vector<CEntity*>
    for (auto Entity : GetEntities()) {
        //printf("EntPosX = %.1f, EntSizeX = %.1f, PosX = %.1f\n", Entity->GetPosition().x, Entity->GetSize().x, Position.x);
        //printf("EntPosY = %.1f, EntSizeY = %.1f, PosY = %.1f\n\n", Entity->GetPosition().y, Entity->GetSize().y, Position.y);
       
        if (Entity->IsSolid() != Solid) {
            continue;
        }
       
        if (Position.y > Entity->GetPosition().y && Position.y < Entity->GetPosition().y + Entity->GetSize().y) {
            if (Position.x < Entity->GetPosition().x) {
                return true;
            }
        }
    }
    return true;
}

I have this utility function but it doesn't work as expected. The vertical Y position works fine (I guess?) but the horizontal X line does not. Can you help me rewrite it correctly?

- regards, fancode992

2

General / Re: Getting intersection direction/side.

« on: December 17, 2019, 05:57:42 pm »

you should use sf::Sprite::getGlobalbounds() instead of the local to test for intersects.
you may try manifold for detecting the collision from every directions up/down or left/right, here an excellent tutorial in this topic with examples:

http://trederia.blogspot.com/2016/02/2d-physics-101-pong.html

Hello Mortal, thank you for helping me .

3

General / Getting intersection direction/side.

« on: December 15, 2019, 08:11:33 pm »

Greetings,
As the title says, how can I get the side a sprite collides with another one? For example, I have an enumeration called "Direction" which includes north, south, west and east, a function shall return only one.

I am currently checking collision between two sprites via this code:

spritevar.getLocalBounds().intersects(spritevar2)

I am sorry for being so undescriptive. Thank you.