java/examples/Topics/Interaction/Reach2/applet/Reach2.java

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+import processing.core.*; 
+
+import java.applet.*; 
+import java.awt.*; 
+import java.awt.image.*; 
+import java.awt.event.*; 
+import java.io.*; 
+import java.net.*; 
+import java.text.*; 
+import java.util.*; 
+import java.util.zip.*; 
+import java.util.regex.*; 
+
+public class Reach2 extends PApplet {
+
+/**
+ * Reach 2. 
+ * Based on code from Keith Peters (www.bit-101.com)
+ * 
+ * The arm follows the position of the mouse by
+ * calculating the angles with atan2(). 
+ */
+
+int numSegments = 10;
+float[] x = new float[numSegments];
+float[] y = new float[numSegments];
+float[] angle = new float[numSegments];
+float segLength = 20;
+float targetX, targetY;
+
+public void setup() {
+  size(200, 200);
+  smooth(); 
+  strokeWeight(20.0f);
+  stroke(0, 100);
+  x[x.length-1] = 0;     // Set base x-coordinate
+  y[x.length-1] = height;  // Set base y-coordinate
+}
+
+public void draw() {
+  background(226);
+  
+  reachSegment(0, mouseX, mouseY);
+  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); 
+  }
+}
+
+public void positionSegment(int a, int b) {
+  x[b] = x[a] + cos(angle[a]) * segLength;
+  y[b] = y[a] + sin(angle[a]) * segLength; 
+}
+
+public 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;
+}
+
+public void segment(float x, float y, float a, float sw) {
+  strokeWeight(sw);
+  pushMatrix();
+  translate(x, y);
+  rotate(a);
+  line(0, 0, segLength, 0);
+  popMatrix();
+}
+
+  static public void main(String args[]) {
+    PApplet.main(new String[] { "Reach2" });
+  }
+}