Hi, I'm following this sdl tutorial by lazyfoo and i want to add a simple jump, like jumping 160px. Here the code for movement;

void Player::handleEvent(SDL_Event& e)
{
	if (e.type == SDL_KEYDOWN && e.key.repeat == 0)
	{
		switch (e.key.keysym.sym)
		{
		case SDLK_UP: _velY -= _playerVel;	break;
		case SDLK_DOWN:	_velY += _playerVel; break;
		case SDLK_LEFT:	_velX -= _playerVel; break;
		case SDLK_RIGHT: _velX += _playerVel; break;
		}
	}

	else if (e.type == SDL_KEYUP && e.key.repeat == 0)
	{
		switch (e.key.keysym.sym)
		{
		case SDLK_UP: _velY += _playerVel; break;
		case SDLK_DOWN:	_velY -= _playerVel; break;
		case SDLK_LEFT: _velX += _playerVel; break;
		case SDLK_RIGHT: _velX -= _playerVel; break;
		}
	}
}

void Player::move(std::vector<vec3Struct>& _levelInfo)
{
	_posX += _velX;
	if( ( _posX < 0 ) || ( _posX + _playerBox > 1000 /*levelWidth*/ ) || touchesWall(_levelInfo))
	{
		_posX -= _velX;
	}

	_posY += _velY;
	if( touchesWall(_levelInfo))
	{
		_posY -= _velY;
	}
}

bool Player::checkCollision( SDL_Rect a, SDL_Rect b )
{
	//The sides of the rectangles
	int leftA, leftB;
	int rightA, rightB;
	int topA, topB;
	int bottomA, bottomB;

	//Calculate the sides of rect A
	leftA = a.x;
	rightA = a.x + a.w;
	topA = a.y;
	bottomA = a.y + a.h;

	//Calculate the sides of rect B
	leftB = b.x;
	rightB = b.x + b.w;
	topB = b.y;
	bottomB = b.y + b.h;

	//If any of the sides from A are outside of B
	if( bottomA <= topB ) {	return false; }
	if( topA >= bottomB ) {	return false; }
	if( rightA <= leftB ) {	return false; }
	if( leftA >= rightB ) {	return false; }
	//If none of the sides from A are outside B
	return true;
}

bool Player::touchesWall(std::vector<vec3Struct>& _levelInfo)
{
	//Go through the tiles
	for( int i = 0; i < _levelInfo.size(); ++i )
	{
		SDL_Rect tmp;
		tmp.x = _levelInfo[i].x;
		tmp.y = _levelInfo[i].y;
		tmp.w = 80;
		tmp.h = 80;

		SDL_Rect _playerRec;
		_playerRec.x = _posX;
		_playerRec.y = _posY;
		_playerRec.w = _playerBox;
		_playerRec.h = _playerBox;

		//If the collision box touches the wall tile
		if( checkCollision( _playerRec, tmp) )
		{
			return true;
		}
	}
	//If no wall tiles were touched
	return false;
}

but everytime a try too add gravity to game, like if player is not toches wall, it y axis will decrease, but i always failed :(

When you say that your attempts to add gravity always fail, in what sense is it failing and how are you adding gravity?

When you say that your attempts to add gravity always fail, in what sense is it failing and how are you adding gravity?

as i said above, if player is not toches wall, it y axis will increases, i add this to the move function

if( !touchesWall(_levelInfo))
	{
		_posY ++;
	}

but, after this, i can no longer move. this fall slowly till it hit the level.

Add gravity by making the character move by applying force, not by changing the coordinates directly.

Edit: I think I got something just for you. Quick and to the point.

http://home.cmit.net/rwolbeck/programmingtutorial/reference/addgravity.htm