Gravity and collision detection in SFML - c++

Question

This is my first attempt with SFML and game development, and I'm having issues with the collision and gravity.
I'm making a 2D platformer game using a tilemap system.
Collision seems to be working(slightly) but is very choppy and I just can't seem to get gravity to work properly. I've tried a few different tutorials but I cant get anything working and I'm at a bit of a loss right now.
If someone could point out what I'm missing here it'd be greatly appreciated!!
Heres the code I'm using for these elements:
In PlayerSprite class(attempt at gravity)
PlayerSprite::PlayerSprite(const sf::Vector2f& size) : AnimatedSprite(size)
{
playerPos = (sf::Vector2f(300.0f, 400.0f));
dead = false;
jumpHeight = 5.f;
scale = 50.f;
accelGravity = 0.5f;
maxGravity = 5.f;
velocity.x = 2.0f;
velocity.y = 2.0f;
playerTexture.loadFromFile("gfx/spritemansheet.png");
setSize(sf::Vector2f(48, 48));
setPosition(playerPos);
setTexture(&playerTexture);
}
PlayerSprite::~PlayerSprite()
{
}
void PlayerSprite::update(float dt)
{
onGround = false;
if (input->isKeyDown(sf::Keyboard::A)) {
input->setKeyUp(sf::Keyboard::A);
playerPos.x -= (dt * step) * 5;
setPosition(playerPos);
//currentAnimation = &walkBack;
}
if (input->isKeyDown(sf::Keyboard::D)) {
input->setKeyUp(sf::Keyboard::D);
playerPos.x += (dt * step) * 5;
setPosition(playerPos);
//currentAnimation = &walk;
}
if (input->isKeyDown(sf::Keyboard::W) ) {
input->setKeyUp(sf::Keyboard::Space);
playerPos.x += (dt * step) * 5;
setPosition(playerPos);
//currentAnimation = &jump;
velocity.y = -5.f * -1;
}
if (onGround == false) {
velocity.y += accelGravity;
if (velocity.y > maxGravity) {
velocity.y = maxGravity;
}
}
if (sf::Mouse::isButtonPressed(sf::Mouse::Left))
{
input->setMouseLeftUp(sf::Mouse::Left);
currentAnimation = &attack;
}
}
void PlayerSprite::setInput(Input* newInp)
{
input = newInp;
}
void PlayerSprite::collisionResponse(Sprite* sp)
{
if (velocity.x > 0) {
velocity.x = 0.f;
}
if (velocity.x < 0) {
velocity.x = 0.f;
}
if (velocity.y > 0) {
velocity.y = 0.f;
onGround = true;
}
if (velocity.y < 0) {
velocity.y = 0.f;
}
setPosition(getPosition().x, sp->getPosition().y - getSize().y);
}
Collision Detection in Game.cpp
void Game::update(float dt)
{
player.update(dt);
manager.update(dt);
std::vector<Tile>* world = worldMap.getScene();
for (int i = 0; i < (int)world->size(); i++) {
if ((*world)[i].isAlive()) {
if (checkGroundBounding(&player, &(*world)[i])) {
player.collisionResponse(&(*world)[i]);
}
}
}
void Game::render() {
beginDraw();
window->draw(bg);
window->draw(player);
manager.render(window);
worldMap.render(window);
endDraw();
}
bool Game::checkGroundBounding(PlayerSprite* b1, Tile* b2)
{
//get radius of sprites
float r1 = b1->getSize().x / 2;
float r2 = b2->getSize().x / 2;
float xposb1 = b1->getPosition().x + r1;
float xposb2 = b2->getPosition().x + r2;
float yposb1 = b1->getPosition().y + r1;
float yposb2 = b2->getPosition().y + r2;
if (pow(xposb2 - xposb1, 2) + pow(yposb2 - yposb1, 2) < pow(r1 + r2, 2)) {
return true;
}
return false;
}

Answer 1

you're collision is super wonky, simply set a oldPos variable to your player position, then do your movement code but only for the X axis, if collision is detected, set the position to oldPos, then set oldPos to the current position again, and repeat for the Y axis:
Pseudocode example:
//X axis
oldPos = position
if(leftKey):
position.x -= speed
if(rightKey):
position.x += speed
if(collision):
position = oldPos
//Y axis
oldPos = position
if(upKey):
position.y -= speed
if(downKey):
position.y += speed
if(collision):
position = oldPos
also you can replace your tile iteration with:
for(Tile t : *world){
t->doStuff();
}
I also don't recommend declaring your tile vector in your update function unless you hate performance