处理塔防游戏 - 塔攻击敌人

我会保持简短，我正在制作一个塔防游戏作为一个迷你项目，同时我有一些空闲时间，我正在尝试弄清楚如何实现塔，以便能够在敌人进入射程时使用 dist 射击敌人但我只是不知道如何实现使用敌人位置和塔位置的方法。我有一个 CreepSprites 和 Towers 的 ArrayList

CreepSprite[] CreepSprites;
ArrayList<Tower> AllTowers = new ArrayList<Tower>();
ArrayList<Creep> AllCreeps = new ArrayList<Creep>();

如果有人能给我一些指导，告诉我如何让塔能够射击小兵，那就太好了，即使它不能消灭它们，只要能够射击它们就太好了。

Cheers

@GoneUp 的答案是正确的。在处理中你有一个名为PVector它还提供了距离方法：dist()

PVector towerPos = new PVector(100, 100);
PVector enemyPos = new PVector(300, 300);

float towerAttackRadius = 200; 


void setup() {
  size(400, 400);
  rectMode(CENTER);
  strokeWeight(3);
}
void draw() {
  background(255);
  //draw tower
  noFill();

  //check range
  if(towerPos.dist(enemyPos) < towerAttackRadius){
    //tower engaged, draw in green
    stroke(0,192,0);
  }else{
    //tower in idle mode, draw in blue
    stroke(0, 0, 192);
  }

  //visualise tower attack radius
  //(towerAttackRadius * 2 -> radius * 2 = diameter (width/height))
  ellipse(towerPos.x, towerPos.y, towerAttackRadius * 2, towerAttackRadius * 2);
  //visualise tower
  rect(towerPos.x, towerPos.y, 30, 30);
  //draw enemy
  stroke(192, 0, 0);
  rect(enemyPos.x, enemyPos.y, 10, 10);
  //instructions
  fill(0);
  text("click and drag to move enemy",10,15);
}

void mouseDragged() {
  enemyPos.set(mouseX, mouseY);
}

我强烈推荐丹尼尔希夫曼的关于向量的代码性质章节。 这是一些线性代数，但它非常有用，特别是对于值得尽早掌握窍门的游戏。

例如，要射击子弹，您需要确定方向。 您可以通过使用向量减法来做到这一点。

此外，您可能想控制子弹在屏幕上朝该方向移动的速度。这也可以通过标准化向量来完成：保持其方向，但将其大小减小到 1.0：

之后，可以轻松地将向量缩放（乘以）到您想要的任何大小。

如果您知道塔的位置，则只需添加此缩放速度即可计算每帧子弹应绘制的位置。

PVector 已经有一个函数可以同时执行以下两个操作：setMag()。 （set mag 是设置幅度（或向量长度）的缩写）

它还提供了一个标题（）方便计算角度的功能。

这是一个基本的概念证明：

PVector towerPos = new PVector(100, 100);
PVector enemyPos = new PVector(300, 300);

float towerAttackRadius = 300; 

ArrayList<Bullet> bullets = new ArrayList<Bullet>(); 

void setup() {
  size(400, 400);
  rectMode(CENTER);
  strokeWeight(3);
}
void draw() {
  background(255);

  //check if an enemy is within range using dist()
  //if the distance is smaller than the radius, attack!
  if(towerPos.dist(enemyPos) < towerAttackRadius){

    //hacky frame based counter: please use a millis() based timer instead
    //shoot every 30 frames
    if(frameCount % 30 == 0){
      shoot();
    }

  }

  //update bullets
  for(Bullet b : bullets) {
    b.update();
  }

  //draw tower
  noFill();
  stroke(0, 0, 192);
  //visualise tower attack radius
  //(towerAttackRadius * 2 -> radius * 2 = diameter (width/height))
  ellipse(towerPos.x, towerPos.y, towerAttackRadius * 2, towerAttackRadius * 2);
  //visualise tower
  rect(towerPos.x, towerPos.y, 30, 30);
  //draw enemy
  stroke(192, 0, 0);
  rect(enemyPos.x, enemyPos.y, 10, 10);
  //instructions
  fill(0);
  text("click and drag to move enemy",10,15);
}

void mouseDragged() {
  enemyPos.set(mouseX, mouseY);
}

void shoot(){
  //make a new Bullet pointing from the tower to the enemy
  Bullet b = new Bullet(towerPos.x,towerPos.y,enemyPos.x,enemyPos.y);
  //add it to the list of bullets (for updates)
  bullets.add(b);

  println(b);
}

class Bullet {
  //where does the bullet shoot from (and it's current position)
  PVector position = new PVector();
  //where does the bullet shooting towards
  PVector target = new PVector();
  //how fast does the bullet move on screen
  float speed = 1.2;
  //how large goes the bullet appear on screen
  float size = 10;

  //bullet velocity
  PVector velocity;

  Bullet(float startX,float startY, float endX, float endY) {
    position.set(startX,startY);
    target.set(endX,endY);

    //compute the difference vector (start to end) = direction
    velocity = PVector.sub(target,position);

    //normalize the vector = same direction but magnitude of 1 -> makes it easy to scale 
    //velocity.normalize();

    //scale by the speed to move on screen)
    //normalize + multiple = resize the vector -> same direction, different length
    //velocity.mult(speed);

    //or do both normalize and multiple using setMag()
    velocity.setMag(speed);  
  }
  void update() {
    //update position based on velocity (simply add velocity to current position)
    position.add(velocity);

    //render
    //compute rotation angle from velocity (implementation is 2D only btw)
    float angle = velocity.heading();
    pushMatrix();
    translate(position.x,position.y);
    rotate(angle);
    stroke(0);
    line(0,0,size,0);
    popMatrix();
  }

  String toString(){
    return position+"->"+target;
  }
}

您实际上可以使用下面的预览来玩：

var towerPos,enemyPos;

var towerAttackRadius = 300; 

var bullets = [];

function setup() {
  createCanvas(400, 400);
  rectMode(CENTER);
  strokeWeight(3);
  
  
  towerPos = createVector(100, 100);
  enemyPos = createVector(300, 300);
}
function draw() {
  background(255);
  
  //check if an enemy is within range using dist()
  //if the distance is smaller than the radius, attack!
  if(towerPos.dist(enemyPos) < towerAttackRadius){
    
    //hacky frame based counter: please use a millis() based timer instead
    //shoot every 30 frames
    if(frameCount % 30 === 0){
      shoot();
    }
    
  }
  
  //update bullets
  for(var i = 0; i < bullets.length; i++) {
    bullets[i].update();
  }

  //draw tower
  noFill();
  stroke(0, 0, 192);
  //visualise tower attack radius 
  //(towerAttackRadius * 2 -> radius * 2 = diameter (width/height))
  ellipse(towerPos.x, towerPos.y, towerAttackRadius * 2, towerAttackRadius * 2);
  //visualise tower
  rect(towerPos.x, towerPos.y, 30, 30);
  //draw enemy
  stroke(192, 0, 0);
  rect(enemyPos.x, enemyPos.y, 10, 10);
  //instructions
  noStroke();
  fill(0);
  text("click and drag to move enemy",10,15);
}

function mouseDragged() {
  enemyPos.set(mouseX, mouseY);
}

function shoot(){
  //make a new Bullet pointing from the tower to the enemy
  var b = new Bullet(towerPos.x,towerPos.y,enemyPos.x,enemyPos.y);
  //add it to the list of bullets (for updates)
  bullets.push(b);
}

function Bullet(startX,startY,endX,endY) {
  //where does the bullet shoot from (and it's current position)
  this.position = createVector(startX,startY);
  //where does the bullet shooting towards
  this.target = createVector(endX,endY);
  //how fast does the bullet move on screen
  this.speed = 1.2;
  //how large goes the bullet appear on screen
  this.size = 10;

  //compute the difference vector (start to end) = direction
  this.velocity = p5.Vector.sub(this.target,this.position);
  //normalize the vector = same direction but magnitude of 1 -> makes it easy to scale 
  this.velocity.normalize();
  //scale by the speed to move on screen)
  //normalize + multiple = resize the vector -> same direction, different length
  this.velocity.mult(this.speed);
  
  this.update = function() {
    //update position based on velocity (simply add velocity to current position)
    this.position.add(this.velocity);
    
    //render
    //compute rotation angle from velocity (implementation is 2D only btw)
    var angle = this.velocity.heading();
    push();
    translate(this.position.x,this.position.y);
    rotate(angle);
    stroke(0);
    line(0,0,this.size,0);
    pop();
  }
  
}


//http://stackoverflow.com/questions/39698472/processing-tower-defence-game-towers-attacking-enemies

<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.5.3/p5.min.js"></script>

祝PVectors 玩得开心！ :) 一个重要的note: 上面的代码是概念证明，并未优化。 从长远来看，有很多塔和敌人，它会减慢速度。 一旦你得到了正确的数学/代码，你就可以开始做一些改进：

• 管理项目符号/实例（例如，重复使用屏幕外的项目符号 而不是一直创建新实例）
• 使用平方距离magSq()相反，使用平方半径来加速计算