c++ - 如何让蛇咬人？

Question

我正在尝试使用 SFML 用 C++ 制作蛇游戏。下面是我的代码。问题是我不知道我怎么可能让蛇咬自己：每个蛇块占据最后一个的位置，从而形成一条完全笔直的蛇。所以这更像是一个算法问题。感谢您的建议 :) BTW 没有将主题标签和 < 放在包含中，因为编辑器将它们带走了：/ BTW2：寻找类似的回复，但没有一个是我的方法或其他语言。干得好：

#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>
#include <SFML/System.hpp>
#include <SFML/Audio.hpp>
#include <deque>

void selfIncrement();

sf::Event event;
sf::Clock clockSnake;
sf::Time elapse;

enum Direction { Up, Down, Left, Right};

int dir = Up;

int n = 1;

class SnakeBlock
{
public:

SnakeBlock * next;
sf::Texture texture;
sf::Sprite snakeblock;
int lastX, lastY;
};

std::deque<SnakeBlock> Snake;

int main()
{
elapse = clockSnake.getElapsedTime();

sf::Music epicMusic;
epicMusic.openFromFile("epicmusic.wav");
epicMusic.play();

SnakeBlock snakeHead;
snakeHead.texture.loadFromFile("spritesheetsnake.png", sf::IntRect(0,0,20,22));
snakeHead.snakeblock.setTexture(snakeHead.texture);
SnakeBlock snakeBody1;
snakeBody1.snakeblock.setTexture(*(snakeHead.snakeblock.getTexture()));
SnakeBlock snakeBody2;
snakeBody2.snakeblock.setTexture(*(snakeHead.snakeblock.getTexture()));

Snake.push_front(snakeHead);
Snake.push_front(snakeBody1);
Snake.push_front(snakeBody2);
Snake[2].snakeblock.setPosition(500,350);
Snake[1].snakeblock.setPosition(475, 338);
Snake[0].snakeblock.setPosition(450, 316);

sf::RenderWindow window(sf::VideoMode(1028,768), "SFML Snake");
window.setFramerateLimit(60);
while(window.isOpen())
{
    while(window.pollEvent(event))
    {
        switch(event.type)
        {
            case sf::Event::Closed:
            epicMusic.stop();
            window.close();
            break;

            default:
            break;
        }

    }

    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Left))
    {
            dir = Left;
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Right))
    {
            dir = Right;
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Down))
    {
            dir = Down;
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Up))
    {
            dir = Up;
    }
    if(dir == Up)
    {

        Snake[0].snakeblock.move(0,-2);
        Snake[n].snakeblock.setPosition(Snake[n-1].snakeblock.getPosition().x, Snake[n-1].snakeblock.getPosition().y+20);
    }
    if(dir == Down)
    {
        Snake[0].snakeblock.move(0,2);
        Snake[n].snakeblock.setPosition(Snake[n-1].snakeblock.getPosition().x, Snake[n-1].snakeblock.getPosition().y-20);
    }
    if(dir == Left)
    {
        Snake[0].snakeblock.move(-2,0);
        Snake[n].snakeblock.setPosition(Snake[n-1].snakeblock.getPosition().x+20, Snake[n-1].snakeblock.getPosition().y);
    }
    if(dir == Right)
    {
        Snake[0].snakeblock.move(2,0);
        Snake[n].snakeblock.setPosition(Snake[n-1].snakeblock.getPosition().x-20, Snake[n-1].snakeblock.getPosition().y);
    }
    window.clear(sf::Color::Red);
    n++;
    if( n > 2)
    {
        n = 1;
    }
    //selfIncrement();
    for(unsigned int m = 0; m < Snake.size(); m++)
    {
        window.draw(Snake[m].snakeblock);
    }

    window.display();
}
return 0;

}

/*void selfIncrement()
{
elapse = clockSnake.getElapsedTime();
if(elapse.asSeconds() > 0.10)
{
    n++;
    clockSnake.restart();
}
if(n > Snake.size())
{
    n = 1;
}
}
*/

使用新原理的新代码::

#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>
#include <SFML/System.hpp>
#include <SFML/Audio.hpp>
#include <deque>

void advanceStep();

sf::Event event;
sf::Clock clockSnake;
sf::Time elapse;

enum Direction { Up, Down, Left, Right};

sf::Vector2i direction;
int dir = Up;

int n = 1;

class SnakeBlock
{
public:

sf::Texture texture;
sf::Sprite snakeblock;
int dir = 0;
int lastX, lastY;
};

SnakeBlock element;
std::deque<SnakeBlock> Snake;

int main()
{
elapse = clockSnake.getElapsedTime();

sf::Music epicMusic;
epicMusic.openFromFile("epicmusic.wav");
epicMusic.play();

SnakeBlock snakeHead;
snakeHead.texture.loadFromFile("spritesheetsnake.png", sf::IntRect(0,0,20,22));
snakeHead.snakeblock.setTexture(snakeHead.texture);
SnakeBlock snakeBody1;
snakeBody1.snakeblock.setTexture(*(snakeHead.snakeblock.getTexture()));
SnakeBlock snakeBody2;
snakeBody2.snakeblock.setTexture(*(snakeHead.snakeblock.getTexture()));

Snake.push_front(snakeHead);
Snake.push_front(snakeBody1);
Snake.push_front(snakeBody2);
Snake[2].snakeblock.setPosition(500,350);
Snake[1].snakeblock.setPosition(475, 338);
Snake[0].snakeblock.setPosition(450, 316);

sf::RenderWindow window(sf::VideoMode(1028,768), "SFML Snake");
window.setFramerateLimit(10);
while(window.isOpen())
{
    while(window.pollEvent(event))
    {
        switch(event.type)
        {
            case sf::Event::Closed:
            epicMusic.stop();
            window.close();
            break;

            default:
            break;
        }

    }

    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Left))
    {
            dir = Left;
            direction.x = -1;
            direction.y = 0;
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Right))
    {
            dir = Right;
            direction.x = 1;
            direction.y = 0;
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Down))
    {
            dir = Down;
            direction.x = 0;
            direction.y = -1;
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Up))
    {
            dir = Up;
            direction.x = 0;
            direction.y = 1;
    }
    if(dir == Up)
    {

        Snake[0].snakeblock.move(0,-2);
        Snake[1].snakeblock.setPosition(Snake[0].snakeblock.getPosition().x, Snake[0].snakeblock.getPosition().y+20);
        Snake[2].snakeblock.setPosition(Snake[1].snakeblock.getPosition().x, Snake[1].snakeblock.getPosition().y+20);
    }
    if(dir == Down)
    {
        Snake[0].snakeblock.move(0,2);
        Snake[1].snakeblock.setPosition(Snake[0].snakeblock.getPosition().x, Snake[0].snakeblock.getPosition().y-20);
        Snake[2].snakeblock.setPosition(Snake[1].snakeblock.getPosition().x, Snake[1].snakeblock.getPosition().y-20);
    }
    if(dir == Left)
    {
        Snake[0].snakeblock.move(-2,0);
        Snake[1].snakeblock.setPosition(Snake[0].snakeblock.getPosition().x+20, Snake[0].snakeblock.getPosition().y);
        Snake[2].snakeblock.setPosition(Snake[1].snakeblock.getPosition().x+20, Snake[1].snakeblock.getPosition().y);
    }
    if(dir == Right)
    {
        Snake[0].snakeblock.move(2,0);
        Snake[1].snakeblock.setPosition(Snake[0].snakeblock.getPosition().x-20, Snake[0].snakeblock.getPosition().y);
        Snake[2].snakeblock.setPosition(Snake[1].snakeblock.getPosition().x-20, Snake[1].snakeblock.getPosition().y);
    }
    window.clear(sf::Color::Red);
    advanceStep();
    for(unsigned int m = 0; m < Snake.size(); m++)
    {
        window.draw(Snake[m].snakeblock);
    }
    window.display();
}
return 0;

}

void advanceStep()
{
sf::Vector2f headpos(Snake[0].snakeblock.getPosition());

headpos.x += 22 * direction.x;
headpos.y += 22 * direction.y;

Snake[0].snakeblock.setPosition(headpos);

Snake.pop_back();
Snake.push_front(Snake[0]);
}

新代码考虑了你们所说的一切，但现在蛇消失了，可能是因为 pop_back..

#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>
#include <SFML/System.hpp>
#include <SFML/Audio.hpp>
#include <deque>

void advanceStep();

sf::Event event;
sf::Clock clockSnake;
sf::Time elapse;

enum Direction { Up, Down, Left, Right};

sf::Vector2i direction(0, 0);
int dir = Up;


class SnakeBlock
{
public:

sf::Texture texture;
sf::Sprite snakeblock;
int dir;
};

std::deque<SnakeBlock> Snake;

int main()
{
elapse = clockSnake.getElapsedTime();

sf::Music epicMusic;
epicMusic.openFromFile("epicmusic.wav");
epicMusic.play();

SnakeBlock snakeHead;
snakeHead.texture.loadFromFile("spritesheetsnake.png", sf::IntRect(0,0,20,22));
snakeHead.snakeblock.setTexture(snakeHead.texture);
SnakeBlock snakeBody1;
snakeBody1.snakeblock.setTexture(*(snakeHead.snakeblock.getTexture()));
SnakeBlock snakeBody2;
snakeBody2.snakeblock.setTexture(*(snakeHead.snakeblock.getTexture()));

Snake.push_back(snakeHead);
Snake.push_back(snakeBody1);
Snake.push_back(snakeBody2);

Snake[2].snakeblock.setPosition(500,350);
Snake[1].snakeblock.setPosition(475, 338);
Snake[0].snakeblock.setPosition(450, 316);

sf::RenderWindow window(sf::VideoMode(1028,768), "SFML Snake");
window.setFramerateLimit(1);
while(window.isOpen())
{
    while(window.pollEvent(event))
    {
        switch(event.type)
        {
            case sf::Event::Closed:
            epicMusic.stop();
            window.close();
            break;

            default:
            break;
        }

    }

    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Left))
    {
            direction.x = -1;
            for(int i = 1; i < Snake.size(); i++)
            {
                Snake[i].snakeblock.setPosition(Snake[i+1].snakeblock.getPosition().x-20, Snake[i+1].snakeblock.getPosition().y);
            }
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Right))
    {
            direction.x = 1;
            for(int j = 1; j < Snake.size(); j++)
            {
                Snake[j].snakeblock.setPosition(Snake[j+1].snakeblock.getPosition().x+20, Snake[j+1].snakeblock.getPosition().y);
            }
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Down))
    {
            direction.y = -1;
            for(int l = 1; l < Snake.size(); l++)
            {
                Snake[l].snakeblock.setPosition(Snake[l+1].snakeblock.getPosition().x, Snake[l+1].snakeblock.getPosition().y-22);
            }
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Up))
    {
            direction.y = 1;
            for(int o = 1; o < Snake.size(); o++)
            {
                Snake[o].snakeblock.setPosition(Snake[o+1].snakeblock.getPosition().x, Snake[o+1].snakeblock.getPosition().y+22);
            }
    }
    window.clear(sf::Color::Red);
    advanceStep();
    for(unsigned int m = 1; m < Snake.size(); m++)
    {
        window.draw(Snake[m].snakeblock);
    }
    window.display();
}
return 0;

}

void advanceStep()
{
sf::Vector2f headpos;
headpos.x = Snake[0].snakeblock.getPosition().x;
headpos.y = Snake[0].snakeblock.getPosition().y;

headpos.x += 22 * direction.x;
headpos.y += 22 * direction.y;

SnakeBlock element;
element.snakeblock.setPosition(headpos);

Snake.pop_back();
Snake.push_front(element);
}

score 3 · Accepted Answer

你的实现有很多问题。这里没有指出每一个问题，而是一个粗略的大纲。假设您的蛇是一个分段列表，具有最大长度：

在每个更新步骤：
1. 下一个位置 = 头部位置 + 当前方向。
2. 在队列头部添加段，在下一个位置。
3. 当队列长度大于最大长度时，删除队列尾部的段。
在键盘输入上，只需更改当前方向。
如果您需要更改蛇的长度，只需更改最大长度 - 然后更新步骤将调整蛇的长度。

从语义上讲，碰撞是指蛇头撞到身体的任何其他部位。

要检测冲突，请在每个更新步骤中执行此操作。检查头部与身体的其余部分。如果有交叉路口，就会发生碰撞。

顺便说一句，如果您希望在最大蛇长度减小时获得更平滑的“收缩”效果，您可以例如每次更新最多删除两个段（队列长度> 最大长度，而删除的段<收缩率）。

编辑：在下面解决您的评论，想知道如何根据整数（或枚举，我看到您现在使用的 - 相同的概念）改变方向；这里还有一些伪代码：

Vec2 direction(0, 0);

if (currentDirection == Up)
    direction.y = -1;
else if (currentDirection == Down)
    direction.y = 1;
else if (currentDirection == Left)
    direction.x = -1;
else if (currentDirection == Right)
    direction.x = 1;

// direction is now a vector containing an x and y offset, which you can
// apply to the current position of the snake head to find the next
// position.

score 2 · Accepted Answer

基本原则是，您需要检测头部是否到达自身的任何块 - 如果是，则它是“自己咬的”。

所以，当你刚刚移动了蛇（包括“生长”它，如果适用的话），检查头部是否与构成蛇的任何其他“块”的位置相匹配。

编辑：要使蛇“摆动”，您需要使用“记住”头部移动的方向，并且每次移动都应将该块的方向“洗牌”到其后面的方向。

换句话说，向中添加一个dir条目SnakeBlock，并使用它来移动每个块。

score 2 · Accepted Answer

这就是你把事情复杂化所得到的。

因为你使用std::deque你不需要“下一个”字段。或“移动”方法。块也不需要单独的纹理（这意味着所有纹理都是唯一的，这是不正确的）。

完整游戏的大致轮廓（构造函数被省略）：

struct Vector2{
   int x, y;
};

typedef std::deque<Vector2> Vec2Deque;

struct Snake{
    Vec2 direction; //(+-1, +-1)
    int blockSize;
    Vec2Deque blocks;//for blocks you only need their coordinates.

    void render(){
        for(size_T i = 0; i < blocks.size(); i++)
             renderSpriteAt(blocks[i]);
    }

    void advanceStep(){
         Vector2 headPos = blocks[0];//take current head pos             
         headPos.x += blockSize * direction.x; //calculate next position based on direction
         headPos.y += blockSize * direction.y; //and block size. Direction is 2component vector.
         blocks.pop_back();//remove last element
         blocks.push_front(headPos);//insert new element with new position as a head. 
              //That'll automatically create illusion of movement.
    }
};

这将模拟经典的基于网格的蛇。

如果您想要更好的蛇（移动平稳，并且可以小角度转动（例如向左旋转 1 度），事情会变得更加复杂。

想得简单。另见 KISS 原则。

新代码考虑了你所说的一切，但现在蛇消失了，可能是因为 pop_back

替换这个：

if(sf::Keyboard::isKeyPressed(sf::Keyboard::Left))
    {
            direction.x = -1;
            for(int i = 1; i < Snake.size(); i++)
            {
                Snake[i].snakeblock.setPosition(Snake[i+1].snakeblock.getPosition().x-20, Snake[i+1].snakeblock.getPosition().y);
            }
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Right))
    {
            direction.x = 1;
            for(int j = 1; j < Snake.size(); j++)
            {
                Snake[j].snakeblock.setPosition(Snake[j+1].snakeblock.getPosition().x+20, Snake[j+1].snakeblock.getPosition().y);
            }
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Down))
    {
            direction.y = -1;
            for(int l = 1; l < Snake.size(); l++)
            {
                Snake[l].snakeblock.setPosition(Snake[l+1].snakeblock.getPosition().x, Snake[l+1].snakeblock.getPosition().y-22);
            }
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Up))
    {
            direction.y = 1;
            for(int o = 1; o < Snake.size(); o++)
            {
                Snake[o].snakeblock.setPosition(Snake[o+1].snakeblock.getPosition().x, Snake[o+1].snakeblock.getPosition().y+22);
            }
    }

有了这个：

if(sf::Keyboard::isKeyPressed(sf::Keyboard::Left))
    {
            direction.x = -1;
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Right))
    {
            direction.x = 1;
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Down))
    {
            direction.y = -1;
            for(int l = 1; l < Snake.size(); l++)
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::Up))
    {
            direction.y = 1;
    }

你不应该在 AdvanceStep 之外的任何地方更新蛇。您应该使用 push/pop 或移动元素的循环，而不是两者。您不知道，您可以在所有循环中使用“i”，并且不需要每次都选择不同的变量名，对吧？

如果您仍然对蛇有疑问，请尝试编写滚动射击游戏。例如：

弹道导弹。
卷轴射手。

除非您想在这些游戏中添加粒子系统，否则它们应该比蛇更容易，因为在这些游戏中，一个对象只有一个精灵。

score 1 · Accepted Answer

据我了解，目前您的蛇仍然是一条直线，您希望它能够像其他游戏一样转动。

我在游戏中所做的，我有两个数据结构，一个用于蛇部分（位置和方向），另一个用于转弯（方向和位置）。

在游戏循环中，Snake 部分沿其方向移动，但如果其位置与转弯方向匹配，则蛇部分将其方向更改为转弯方向并相应地更新其位置。

当您将其应用于蛇的尾部时，会移除转弯。并添加当您检测到按键时，捕获其方向和位置是蛇的头部位置。

我的实现在这里，你可以看看我在说什么。

c++ - 如何让蛇咬人？

4 回答 4

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