spring– 如何在使用粒子系统处理中制作滑动构件

概述我在Processing中模拟粒子系统.基于丹尼尔希夫曼的“本质的代码”一书,我做了一个d簧,然后我开始尝试使用滑块做一个基于滑块的长度更长或更短的滑块.现在,我试图制作一个滑块滑动,两个粒子移动到两个粒子的相同方向.我使用PVector添加,找到新位置并绘制节点,但是当我有多个成员且一个受其他成员影响时它不起作用.我需要使用一个force来执行此 *** 作：请参

我在Processing中模拟粒子系统.基于丹尼尔希夫曼的“本质的代码”一书,我做了一个d簧,然后我开始尝试使用滑块做一个基于滑块的长度更长或更短的滑块.

现在,我试图制作一个滑块滑动,两个粒子移动到两个粒子的相同方向.
我使用PVector添加,找到新位置并绘制节点,但是当我有多个成员且一个受其他成员影响时它不起作用.
我需要使用一个force来执行此 *** 作：请参阅applyForce()函数.

voID update(float distance) {  PVector force = PVector.sub(b.location,a.location);   float d = force.mag();  float x = d - distance; //direction of the force  force.normalize();  force.mult(-1 * k* x/mass); //apply to one node  b.applyForce(force);   force.mult(-1); //apply opposite to the other node  a.applyForce(force);}//Newton's law: F = M * AvoID applyForce(PVector force) {  PVector f = force.get();  f.div(mass);  acceleration.add(f);}

检查下图：

(a)是我想要的,(b)它现在是怎么做的.

在第一个例子中,长度相同,成员滑动(两个粒子).

在第二个中,长度更大并且不会滑动

如果您知道如何施加滑动构件的力,请告诉我.

谢谢

最佳答案如果我理解正确,你会尝试做一些事情：

>改变d簧的长度
>在春天的方向上翻译d簧的端点
>使用滑块控制上述参数

第一部分是微不足道的,因为Spring对象具有len属性.
第二个涉及一点vector math：

>一条线的方向是减去它的两个端点
>通过首先对其进行归一化(将其减小以使其长度等于1.0)然后乘以标量值,可以轻松地将矢量缩放到任何长度.
>可以通过简单地向其自身添加另一个向量来翻译向量

这是一个注释草图,实现了以上几点：

//slIDers to control spring rest length and translationSlIDer rlength = new SlIDer("rest length",5,200,20,50,250,100,false);SlIDer translate = new SlIDer("translate",30,-10,10,false);Spring spring = new Spring(new Bob(75,350),new Bob(350,75),(int)rlength.value);voID setup(){  size(400,400);  spring.k = 0.01;//tweak elasticity}voID draw(){  //  update  //update slIDers  rlength.update(mouseX,mouseY,mousepressed);  translate.update(mouseX,mousepressed);  //update spring  spring.a.update();  spring.b.update();  spring.update();  //make both points draggable  spring.a.drag(mouseX,mouseY);  spring.b.drag(mouseX,mouseY);  //draw  background(255);  rlength.draw();  translate.draw();  spring.display();}//handle mouse events for spring points draggingvoID mousepressed() {  spring.a.clicked(mouseX,mouseY);  spring.b.clicked(mouseX,mouseY);}voID mouseReleased() {  spring.a.stopDragging();  spring.b.stopDragging();}//handle slIDer eventsvoID onSlIDerUpdate(SlIDer s){  if(s == rlength) spring.len = rlength.value;  if(s == translate){    //compute the direction of the spring by subtracting the two points    PVector direction = PVector.sub(spring.a.location,spring.b.location);    //normalize the vector -> it will not have a length/magnitude of 1.0,but will still point in the line direction    direction.normalize();    //scale or multiply the normalized vector to the translation amount    direction.mult(translate.value);    //finally,add the result to each spring point,essentially offsetting/translating    spring.a.location.add(direction);    spring.b.location.add(direction);  } }//SlIDerclass GUIElement{  float w,h,x,y;//wIDth,height and position  color bg = color(200);//background colour  color fg = color(0);//foreground colour  String label;  GUIElement(String label,float x,float y,float w,float h){    this.x = x;    this.y = y;    this.w = w;    this.h = h;    this.label = label;  }  voID update(int mx,int my,boolean md){}  voID draw(){}}class SlIDer extends GUIElement{  float min,max,value,pvalue;//slIDer values: minimum,maximum and current  float cx,pw = 20;//current slIDer picker position,picker wIDth  boolean updating,liveDrag = true,isInt = false;  //label to display on slIDer,it's position(x,y),size(w,h) and values(min,max and default/current)  SlIDer(String label,float h,float min,float max,float value,boolean isInt){    super(label,y,w,h);    this.min = min;    this.max = max;    this.value = value;    this.isInt = isInt;    cx = map(value,min,x+w);  }  voID update(int mx,boolean md){    if(md){      if((mx >= x && mx <= (x+w)) &&         (my >= y && my <= (y+h))){        cx = mx;        value = map(cx,x+w,max);        updating = true;        if(liveDrag){          boolean updated = (isInt ? ((int)value != (int)pvalue) : (value != pvalue));          if(updated){            pvalue = value;            onSlIDerUpdate(this);          }        }      }else updating = false;    }else{      if(updating){        updating = false;        onSlIDerUpdate(this);      }      }  }  voID draw(){    pushStyle();    nostroke();    fill(bg);    rect(x,h);    fill(fg,64);    rect(x,cx-x,h);//this displays a rect that stretches based on the value    fill(0);    text(label+": "+(isInt ? (int)value : value),x+pw,y+h*.75);    popStyle();  }  String toString(){    return label + ":" + value;  }}// The Nature of Code// DanIEl Shiffman// http://natureofcode.com// Bob class,just like our regular Mover (location,veLocity,acceleration,mass)class Bob {   PVector location;  PVector veLocity;  PVector acceleration;  float mass = 12;  // Arbitrary damPing to simulate friction / drag   float damPing = 0.95;  // For mouse interaction  PVector dragOffset;  boolean dragging = false;  // Constructor  Bob(float x,float y) {    location = new PVector(x,y);    veLocity = new PVector();    acceleration = new PVector();    dragOffset = new PVector();  }   // Standard Euler integration  voID update() {     veLocity.add(acceleration);    veLocity.mult(damPing);    location.add(veLocity);    acceleration.mult(0);  }  // Newton's law: F = M * A  voID applyForce(PVector force) {    PVector f = force.get();    f.div(mass);    acceleration.add(f);  }  // Draw the bob  voID display() {     stroke(0);    strokeWeight(2);    fill(175);    if (dragging) {      fill(50);    }    ellipse(location.x,location.y,mass*2,mass*2);  }   // The methods below are for mouse interaction  // This checks to see if we clicked on the mover  voID clicked(int mx,int my) {    float d = dist(mx,my,location.x,location.y);    if (d < mass) {      dragging = true;      dragOffset.x = location.x-mx;      dragOffset.y = location.y-my;    }  }  voID stopDragging() {    dragging = false;  }  voID drag(int mx,int my) {    if (dragging) {      location.x = mx + dragOffset.x;      location.y = my + dragOffset.y;    }  }}// Nature of Code 2011// DanIEl Shiffman// Chapter 3: Oscillation// Class to describe an anchor point that can connect to "Bob" objects via a spring// Thank you: http://www.myphysicslab.com/spring2d.HTMLclass Spring {   // Location  PVector anchor;  // Rest length and spring constant  float len;  float k = 0.2;  Bob a;  Bob b;  // Constructor  Spring(Bob a_,Bob b_,int l) {    a = a_;    b = b_;    len = l;  }   // Calculate spring force  voID update() {    // Vector pointing from anchor to bob location    PVector force = PVector.sub(a.location,b.location);    // What is distance    float d = force.mag();    // Stretch is difference between current distance and rest length    float stretch = d - len;    // Calculate force according to Hooke's Law    // F = k * stretch    force.normalize();    force.mult(-1 * k * stretch);    a.applyForce(force);    force.mult(-1);    b.applyForce(force);  }  voID display() {    strokeWeight(3);    stroke(0);    line(a.location.x,a.location.y,b.location.x,b.location.y);    ellipse(a.location.x,10);    ellipse(b.location.x,b.location.y,10);  }}

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