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Fish-eye view of a force-directed graph

[0 Replies]
- 20-Jun-2013 09:59 AM
- Forum: Programming Questions
Hi All,

I'm trying to make a 2D fish-eye view of a force-directed graph. The problem I'm having is that whenever I change the position of the nodes to reflect an observer looking from a certain distance, the attraction of the nodes make them flock together, thereby ruining the fish-eye effect. It looks fine for a split second, but then they attract each other very quickly.

Any idea how to fix that?

The code is the following:
1. ArrayList<Node> nodes = new ArrayList();
2. ArrayList<Spring> springs = new ArrayList();
4. int nnodes = 200;
6. boolean fishEyeView = false;
7. float observerRadius;
8. PVector center;
10. void setup() {
11. size(800, 800);
12. center = new PVector(width/2, height/2);
13. observerRadius = min(width, height) / 2;
14. background(255);
15. initNodesAndSprings();
16. smooth();
17. }
19. void draw() {
20. background(255);
22. for (Node n : nodes) {
23. n.attract(nodes);
24. n.update();
25. n.render();
26. }
28. for (Spring s : springs) {
29. s.update();
30. s.render();
31. }
32. }
34. void initNodesAndSprings() {
35. for (int i = 0; i < nnodes; i++) {
36. nodes.add(new Node(width/2 + random(-200, 200), height/2 + random(-200, 200), floor(random(10, 20))));
37. }
38. for (int j = 0; j < nodes.size()-1; j++) {
39. int rCount = floor(random(1, 2));
40. for (int i = 0; i < rCount; i++) {
41. int r = floor(random(j+1, nodes.size()));
42. Spring newSpring = new Spring(nodes.get(j), nodes.get(r));
43. newSpring.length = 20;
44. newSpring.stiffness = 1;
45. springs.add(newSpring);
46. }
47. }
48. }
50. void keyPressed() {
51. if (key == ' ') fishEyeView = !fishEyeView;
52. }
54. class Node {
55. String id;
56. float rad;
57. float scaling = 1;
59. float minX, maxX, minY, maxY;
61. PVector pos;
62. PVector velocity = new PVector(0, 0);
63. float maxVelocity = 10;
65. float damping = 0.5;
66. float radius = 100;
67. float strength = -5; // Negative ensures repulsion
68. float ramp = 1.0;
70. Node(float x, float y, int rad) {
71. pos = new PVector(x, y);
72. pos = new PVector(x, y);
73. this.rad = rad;
74. minX = rad;
75. maxX = width - rad;
76. minY = rad;
77. maxY = height - rad;
78. }
80. void attract(ArrayList<Node> nodes) {
81. for (Node n : nodes) {
82. if (n == null) break; // stop when empty
83. if (n == this) continue; // not with itself
84. float d = PVector.dist(pos, n.pos);
85. if (d > 0 && d < radius) {
86. float s = pow(d / radius, 1 / ramp);
87. float f = s * 9 * strength * (1 / (s + 1) + ((s - 3) / 4)) / d;
88. PVector df = PVector.sub(pos, n.pos);
89. df.mult(f);
90. n.velocity.add(df);
91. }
92. }
93. }
95. void update() {
96. velocity.limit(maxVelocity);
97. pos.add(velocity);
98. velocity.mult(1 - damping);
99. if (fishEyeView) {
100. screenPos();
101. } else {
102. scaling = 1;
103. }
104. }
106. void render() {
107. pushMatrix();
108. translate(pos.x, pos.y);
109. fill(50);
110. ellipse(0, 0, (rad + 8) * scaling, (rad + 8) * scaling);
111. stroke(255);
112. strokeWeight(2);
113. fill(0);
114. ellipse(0, 0, rad * scaling, rad * scaling);
115. fill(255);
116. ellipse(0, 0, 0.1 * scaling, 0.1 * scaling);
117. popMatrix();
118. }
120. void screenPos() {
121. PVector centerToPos = PVector.sub(pos, center);
122. float distanceToCenter = centerToPos.mag();
123. float viewingAngle = atan(distanceToCenter / observerRadius);
124. float newDistanceToCenter = viewingAngle * observerRadius;
125. centerToPos.normalize();
126. centerToPos.mult(newDistanceToCenter);
127. scaling = map(viewingAngle, 0, HALF_PI, 1, 0.2);
128. pos = PVector.add(center, centerToPos);
129. }
130. }
132. class Spring {
133. Node from;
134. Node to;
136. float length = 100;
137. float stiffness = 0.6;
138. float damping = 0.9;
140. Spring(Node from, Node to) {
141. this.from = from;
142. this.to = to;
143. }
145. void update() {
146. PVector diff = PVector.sub(to.pos, from.pos);
147. diff.normalize();
148. diff.mult(length);
149. PVector target = PVector.add(from.pos, diff);
151. PVector force = PVector.sub(target, to.pos);
152. force.mult(0.5);
153. force.mult(stiffness);
154. force.mult(1 - damping);
156. to.velocity.add(force);
157. from.velocity.add(PVector.mult(force, -1));
158. }
160. void render() {
161. stroke(0, 130, 164);
162. strokeWeight(1);
163. line(from.pos.x, from.pos.y, to.pos.x, to.pos.y);
164. }
165. }

Apache's HttpClient suite not working - Ben Fry's "Data visualization" chap. 9

[5 Replies]
- 08-Jul-2012 12:26 PM
- Forum: Contributed Library Questions
Hi All,

I'm reading Ben Fry's book "Data visualization" and in Chapter 9 "Acquiring data" there's a section on Apache's HttpClient suite to easily download the content of a webpage.

The book provides the code, specifying that we first need to download three .jar files for the code to work properly. These files are available from Apache's HttpClient project webpage.

Ben then goes on to explain that we just need to put these .jar files into the same sketch folder containing our code and that it will work (he doesn't say we have to put the .jar files into the libraries folder).

Unfortunately I did exactly what he says but it doesn't work. I've got an error message telling me Processing can't find the libraries I'm trying to import:

import org.apache.commons.httpclient.*;

import org.apache.commons.httpclient.methods.*;

import org.apache.log4j.*;

Error message: "The package 'org.apache.commons' does not exist. You might be missing a library.

Can anyone help me with this?

Many thanks in advance

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