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graphic-processing-site-examples-Topics-Interaction-Reach3-Reach3.pde / pde



  
Reach 3. Based on code from Keith Peters (www.bit-101.com) The arm follows the position of the ball by calculating the angles with atan2().

  
  
  int numSegments = 6;
  float[] x = new float[numSegments];
  float[] y = new float[numSegments];
  float[] angle = new float[numSegments];
  float segLength = 15;
  float targetX, targetY;
  
  float ballX = 50;
  float ballY = 50;
  int ballXDirection = 1;
  int ballYDirection = -1;
  
  void setup() {
    size(200, 200);
    smooth(); 
    strokeWeight(20.0);
    stroke(0, 100);
    noFill();
    x[x.length-1] = width/2;     // Set base x-coordinate
    y[x.length-1] = height;  // Set base y-coordinate
  }
  
  void draw() {
    background(226);
    
    strokeWeight(20);
    ballX = ballX + 1.0 * ballXDirection;
    ballY = ballY + 0.8 * ballYDirection;
    if(ballX > width-25 || ballX < 25) {
      ballXDirection *= -1; 
    }
    if(ballY > height-25 || ballY < 25) {
      ballYDirection *= -1; 
    }
    ellipse(ballX, ballY, 30, 30);
    
    reachSegment(0, ballX, ballY);
    for(int i=1; i<numSegments; i++) {
      reachSegment(i, targetX, targetY);
    }
    for(int i=x.length-1; i>=1; i--) {
      positionSegment(i, i-1);  
    } 
    for(int i=0; i<x.length; i++) {
      segment(x[i], y[i], angle[i], (i+1)*2); 
    }
  }
  
  void positionSegment(int a, int b) {
    x[b] = x[a] + cos(angle[a]) * segLength;
    y[b] = y[a] + sin(angle[a]) * segLength; 
  }
  
  void reachSegment(int i, float xin, float yin) {
    float dx = xin - x[i];
    float dy = yin - y[i];
    angle[i] = atan2(dy, dx);  
    targetX = xin - cos(angle[i]) * segLength;
    targetY = yin - sin(angle[i]) * segLength;
  }
  
  void segment(float x, float y, float a, float sw) {
    strokeWeight(sw);
    pushMatrix();
    translate(x, y);
    rotate(a);
    line(0, 0, segLength, 0);
    popMatrix();
  }
  


(C) Æliens 20/2/2008

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