PGraphics pg1, pg2;
PVector Dot_A = new PVector(130, 300); //点Aを定義
PVector Dot_D = new PVector(390, 360); //点Dを定義
PVector Dot_B;
PVector Dot_C;

float theta_A = 0; //θAを初期化
float theta_B, theta_D, phi_B;
float r = 15;
float s;

void setup() {
  size(500, 500);
  background(255);
  //PGraphicsを生成
  pg1 = createGraphics(500, 500);
  pg2 = createGraphics(500, 500);
}

void draw() {
  background(255);
  update(100, 280, 200); //辺a=100,b=280,c=200
  display();
  
}

void update(float a, float b, float c) {
  //点Bの位置
  float x_b = 130 + a * cos(theta_A);
  float y_b = 300 + a * sin(theta_A);
  Dot_B = new PVector(x_b, y_b);
  
  s = dist(Dot_B.x, Dot_B.y, Dot_D.x, Dot_D.y); //辺BDを計算
  
  theta_D = asin((a * sin(theta_A)) / s); //θDを計算
  phi_B = -acos((sq(b)+sq(s)-sq(c)) / (2 * b * s)); //φBを計算
  theta_B = phi_B - theta_D; //θBを計算
  
  //点Cの位置
  float x_c = Dot_B.x + b * cos(theta_B);
  float y_c = Dot_B.y + b * sin(theta_B);
  Dot_C = new PVector(x_c, y_c);
  
  theta_A += 0.03; //θAを更新して回転
}

void display() {
  //リンクを生成
  stroke(0);
  strokeWeight(2);
  line(Dot_A.x, Dot_A.y, Dot_B.x, Dot_B.y);
  line(Dot_B.x, Dot_B.y, Dot_C.x, Dot_C.y);
  line(Dot_C.x, Dot_C.y, Dot_D.x, Dot_D.y);
  
  //各点を生成
  noStroke();
  fill(0);
  ellipse(Dot_A.x, Dot_A.y, r, r);
  ellipse(Dot_D.x, Dot_D.y, r, r);
  
  fill(209, 41, 26);
  ellipse(Dot_B.x, Dot_B.y, r, r);
  
  fill(0, 40, 205);
  ellipse(Dot_C.x, Dot_C.y, r, r);
}
boolean showDriver = false;
boolean showFollower = false;
boolean showLine_s = false;

//原動節の軌跡
void Driver() {
  pg1.beginDraw();
  pg1.noStroke();
  pg1.fill(209, 41, 26);
  pg1.ellipse(Dot_B.x, Dot_B.y, 5, 5);
  pg1.endDraw();
  image(pg1, 0, 0);
}

//従動節の軌跡
void Follower() {
  pg2.beginDraw();
  pg2.noStroke();
  pg2.fill(0, 40, 205);
  pg2.ellipse(Dot_C.x, Dot_C.y, 5, 5);
  pg2.endDraw();
  image(pg2, 0, 0);
}

void Line_s() {
  stroke(0);
  line(Dot_B.x, Dot_B.y, Dot_D.x, Dot_D.y);
}

void keyPressed() {
  if (key == 'b') {
    showDriver = !showDriver;
    if (!showDriver) showDriver = false;
  } else if (key == 'c') {
    showFollower = !showFollower;
    if (!showFollower) showFollower = false;
  } else if (key == 's') {
    showLine_s = !showLine_s;
    if (!showLine_s) showLine_s = false;
  }
}