这段代码做了什么（SFML C ++游戏）？ [英] What does this piece of code does(SFML C++ game)?

问题描述

大家好，

我正在尝试用SFML做一个简单的乒乓球游戏。



我被困在一块我从互联网上拿出的代码，我无法理解详细的工作，所以请大家解释一下。



下面的代码是移动一个球随机方向，当它击中边界或划桨时使其反弹

Hello guys,
I am trying to make a simple ping pong game using SFML.

I am stuck with a piece of code which I took out from internet, I am not able to understand the working in detail so guys please explain.

Below piece of code is to move a ball in a random direction and make it bounce when it hits the boundary or a paddle

<pre lang="c++">
void update(sf::Clock &clock, sf::Time &elapsed) {

		const float velocity = std::sqrt(direction.x * direction.x + direction.y * direction.y);

		elapsed += clock.restart();
		while (elapsed >= update_ms) {
			const auto pos = ball.getPosition();
			const auto delta = update_ms.asSeconds() * velocity;
			sf::Vector2f new_pos(pos.x + direction.x * delta, pos.y + direction.y * delta);

			if (new_pos.x - ball_radius < 0) { // left window edge
				direction.x *= -1;
				new_pos.x = 0 + ball_radius;
			}
			else if (new_pos.x + ball_radius >= 800) { // right window edge
				direction.x *= -1;
				new_pos.x = 800 - ball_radius;
			}
			else if (new_pos.y - ball_radius < 0) { // top of window
				direction.y *= -1;
				new_pos.y = 0 + ball_radius;
			}
			else if (new_pos.y + ball_radius >= 500) { // bottom of window
				direction.y *= -1;
				new_pos.y = 500 - ball_radius;
			}
			ball.setPosition(new_pos);

			elapsed -= update_ms;
		}
	}

我编辑了我的愿望。我已经将一个时钟和vector2f方向引用到一个私有变量，这将使球以随机方向射击。



我尝试过：



理解了一下代码，但不详细，所以需要你的帮助。

I have edited to code to my wish a bit. I have given a reference to a clock and vector2f direction to a private variable which will make the ball shoot in a random direction.

What I have tried:

Understood the code a bit, but not in detail so need your help guys.

推荐答案

此类代码使用以下公式更新球的位置：

Such code updates the ball position, using the following formula:

new_position = current_position + current_speed * delta_time

然后检查新位置是否会越过边界，在这种情况下它会使球反弹，恢复速度并更新其位置。

Then it checks if the new position would cross a boundary, in such a case it makes the ball bounce, reverting the speed and updating its position.

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