I've been searching around for information on how to recognize facial expressions in Processing, and as far as I can tell, there is no previous work on the subject. It seems like there would be, but I just can't find it. Does anyone else know about a project or a library that I can start from?

My short term goal is to program a mimic that sees your face in the webcam and copies your expression to a smiley-face kind of illustration. Concurrently I'd implement a hardware version of the smiley. I hope to ultimately add some intelligence to the face, where it might attempt to interact rather than just react.

If I can't find anything Processing specific, I guess I will have to use OpenCV or something like that to detect eyes, eyebrows, mouth, etc. and write some algorithms to determine their expression. I have not yet searched for recognizing facial expressions in general, and any guidance would be appreciated (though I understand it's beyond the scope of this forum).

Thanks for your help.

I am getting a NullPointerException when I use a mouseClicked() to add a new object to an array. I think it's a scope problem or perhaps the mouseClicked() event is happening in the middle of something causing confusion. My sketch models some charged particles moving around in 2 dimensions. When you click, it is supposed to add a new particle of random charge polarity where you click. I can't really see what the problem is specifically, though. Perhaps it's obvious to someone around here.

Thanks

1. // Global Declarations.
2. int backgroundColor = 200;
3. int noOfParticles = 0;
4. // Temporary value to hold the field strength.
5. float tempFieldStrength;
6. Particle[] particles;
7. // PVector holding a temporary field.
8. PVector tempFieldVector;
9. 
   
10. // Setup Function.
11. void setup() {
12.   size(640, 480);
13.   particles = new Particle[16];
14.   particles[0] = new Particle(10, -10, 300, 200);
15.   noOfParticles++;
16.   particles[1] = new Particle(10, -10, 400, 400);
17.   noOfParticles++;
18.   particles[2] = new Particle(10, 10, 500, 300);
19.   noOfParticles++;
20.   particles[3] = new Particle(10, 10, 100, 100);
21.   noOfParticles++;
22. }
23. 
    
24. // Main Program Loop.
25. void draw() {
26.   background(backgroundColor);
27.   // Locate particles.
28.   for (int i = 0; i < noOfParticles; i++) {
29.     particles[i].updateLocation(); // Here's where Processing highlights the crash...
30.   }
31.   // Draw particles.
32.   for (int i = 0; i < noOfParticles; i++) {
33.     particles[i].drawParticle();
34.   }
35.   // Update particle velocity.
36.   for (int i = 0; i < noOfParticles; i++) {
37.     particles[i].updateVelocity(i);
38.   }
39. }
40. 
    
41. void mouseClicked() {
42.   // Random charge
43.   float polarity = random(-1, 1);
44.   if (polarity > 0) polarity = 10;
45.   if (polarity < 0) polarity = -10;
46.   noOfParticles++;
47.   particles[noOfParticles+1] = new Particle(10, int(polarity), mouseX, mouseY);
48. }
49. 
    
50. class Particle {
51.   // Fields
52.   // The particle's mass.
53.   float mass;
54.   // The particle's charge.
55.   float charge;
56.   // The particle's physical size.
57.   int dia;
58.   // PVector representing particle location.
59.   PVector loc;
60.   // PVector representing particle velocity.
61.   PVector v;
62.   
63.   // Constructor
64.   Particle(float m, int c, int x, int y) {
65.     // How the constructor is called will determine the particle mass and charge.
66.     mass = m;
67.     charge = c;
68.     // The location of each new particle is chosen by the main program.
69.     loc = new PVector(x, y);
70.     // The velocity of all particles starts out at 0.
71.     v = new PVector(0, 0);
72.     tempFieldVector = new PVector(0, 0);
73.   }
74.   
75.   // Methods
76.   void drawParticle() {
77.     noStroke();
78.     // Particle fill color will be based on the charge.
79.     if (charge > 0) fill(255);
80.     if (charge < 0) fill(0);
81.     // Draw the particle at it's location vector.
82.     ellipse(loc.x, loc.y, int(mass), int(mass));
83.   }
84.   void updateVelocity(int whichOne) {
85.     // Velocity changes based on the pull of all the other particles.
86.     for (int i = 0; i < noOfParticles; i++) {
87.       if (whichOne != i) {
88.         // Add to the velocity vector the force due to each particle.
89.         tempFieldVector.x = loc.x - particles[i].loc.x;
90.         tempFieldVector.y = loc.y - particles[i].loc.y;
91.         tempFieldStrength = charge * particles[i].charge / sq(tempFieldVector.mag());
92.         tempFieldVector.normalize();
93.         tempFieldVector.mult(tempFieldStrength / mass);
94.         v.add(tempFieldVector);
95.       }
96.     }
97.   }
98.   void updateLocation() {
99.     // The location vector is based on the old location plus the velocity.
100.     loc.add(v);
101.   }
102. }