java - 如何给双摆添加鼠标拖动功能

Question

我有一个双摆的代码，它使用摆的前一个位置用一条线跟踪第二个摆的中心。我需要添加一个功能，当鼠标被点击时(在钟摆上或不在钟摆上，这无关紧要)，钟摆可以在钟摆的边界内在屏幕上拖动，我不确定鼠标拖动()是否有效或者我是否应该为钟摆使用一个类以使其更容易

float r1 = 200;
float r2 = 200;
float m1 = 40;
float m2 = 40;
float a1 = PI/2;
float a2 = PI/2;
float a1_v = 0;
float a2_v = 0;
float g = 1;

float px2 = -1;
float py2 = -1;
float cx, cy;

PGraphics canvas;

void setup() {
  size(900, 600);
  cx = width/2;
  cy = 200;
  canvas = createGraphics(width, height);
  canvas.beginDraw();
  canvas.background(255);
  canvas.endDraw();
}

void draw() {
  background(255);
  imageMode(CORNER);
  image(canvas, 0, 0, width, height);

  float num1 = -g * (2 * m1 + m2) * sin(a1);
  float num2 = -m2 * g * sin(a1-2*a2);
  float num3 = -2*sin(a1-a2)*m2;
  float num4 = a2_v*a2_v*r2+a1_v*a1_v*r1*cos(a1-a2);
  float den = r1 * (2*m1+m2-m2*cos(2*a1-2*a2));
  float a1_a = (num1 + num2 + num3*num4) / den;

  num1 = 2 * sin(a1-a2);
  num2 = (a1_v*a1_v*r1*(m1+m2));
  num3 = g * (m1 + m2) * cos(a1);
  num4 = a2_v*a2_v*r2*m2*cos(a1-a2);
  den = r2 * (2*m1+m2-m2*cos(2*a1-2*a2));
  float a2_a = (num1*(num2+num3+num4)) / den;

  translate(cx, cy);
  stroke(0);
  strokeWeight(2);

  float x1 = r1 * sin(a1);
  float y1 = r1 * cos(a1);

  float x2 = x1 + r2 * sin(a2);
  float y2 = y1 + r2 * cos(a2);


  line(0, 0, x1, y1);
  fill(0);
  ellipse(x1, y1, m1, m1);

  line(x1, y1, x2, y2);
  fill(0);
  ellipse(x2, y2, m2, m2);

  a1_v += a1_a;
  a2_v += a2_a;
  a1 += a1_v;
  a2 += a2_v;

  // a1_v *= 0.99;
  // a2_v *= 0.99;

  canvas.beginDraw();
  //canvas.background(0, 1);
  canvas.translate(cx, cy);
  canvas.stroke(0);
  if (frameCount > 1) {
    canvas.line(px2, py2, x2, y2);
  }
  canvas.endDraw();


  px2 = x2;
  py2 = y2;
}

Answer 1

你在正确的轨道上:cx 和 cy 是系统原点的坐标。

只需在 mouseDragged() 回调中将它们更新为鼠标坐标:

void mouseDragged(){
  cx = mouseX;
  cy = mouseY;
}

要解决您在评论中阐明的问题，一个快速而肮脏的选择是简单地用鼠标坐标覆盖 x2,y2(由 cx,cy 系统原点位置偏移):

float x2 = 0;
  float y2 = 0;

  if(mousePressed){
    x2 = mouseX - cx;
    y2 = mouseY - cy;
  }else{
    x2 = x1 + r2 * sin(a2);
    y2 = y1 + r2 * cos(a2);  
  }

这是应用了上述内容的完整代码 list :

float r1 = 200;
float r2 = 200;
float m1 = 40;
float m2 = 40;
float a1 = PI/2;
float a2 = PI/2;
float a1_v = 0;
float a2_v = 0;
float g = 1;

float px2 = -1;
float py2 = -1;
float cx, cy;

PGraphics canvas;

void setup() {
  size(900, 600);
  cx = width/2;
  cy = 200;
  canvas = createGraphics(width, height);
  canvas.beginDraw();
  canvas.background(255);
  canvas.endDraw();
}

void draw() {
  background(255);
  imageMode(CORNER);
  image(canvas, 0, 0, width, height);

  float num1 = -g * (2 * m1 + m2) * sin(a1);
  float num2 = -m2 * g * sin(a1-2*a2);
  float num3 = -2*sin(a1-a2)*m2;
  float num4 = a2_v*a2_v*r2+a1_v*a1_v*r1*cos(a1-a2);
  float den = r1 * (2*m1+m2-m2*cos(2*a1-2*a2));
  float a1_a = (num1 + num2 + num3*num4) / den;

  num1 = 2 * sin(a1-a2);
  num2 = (a1_v*a1_v*r1*(m1+m2));
  num3 = g * (m1 + m2) * cos(a1);
  num4 = a2_v*a2_v*r2*m2*cos(a1-a2);
  den = r2 * (2*m1+m2-m2*cos(2*a1-2*a2));
  float a2_a = (num1*(num2+num3+num4)) / den;

  translate(cx, cy);
  stroke(0);
  strokeWeight(2);

  float x1 = r1 * sin(a1);
  float y1 = r1 * cos(a1);

  float x2 = 0;
  float y2 = 0;

  if(mousePressed){
    x2 = mouseX - cx;
    y2 = mouseY - cy;
  }else{
    x2 = x1 + r2 * sin(a2);
    y2 = y1 + r2 * cos(a2);  
  }

  line(0, 0, x1, y1);
  fill(0);
  ellipse(x1, y1, m1, m1);

  line(x1, y1, x2, y2);
  fill(0);
  ellipse(x2, y2, m2, m2);

  a1_v += a1_a;
  a2_v += a2_a;
  a1 += a1_v;
  a2 += a2_v;

  // a1_v *= 0.99;
  // a2_v *= 0.99;

  canvas.beginDraw();
  //canvas.background(0, 1);
  canvas.translate(cx, cy);
  canvas.stroke(0);
  if (frameCount > 1) {
    canvas.line(px2, py2, x2, y2);
  }
  canvas.endDraw();


  px2 = x2;
  py2 = y2;
}

请记住，这只会让您在视觉上拖动第二个球，完全忽略模拟。当您释放鼠标时，模拟将恢复。如果您确实想从下到上影响模拟，则需要进行数学运算(在您的情况下为第 32-44 行)。