int screen_width = 340;
int screen_height = 280;
int num_particles = 1000;
float[] particles = new float[num_particles*2];
float[] vel = new float[num_particles*2];

void setup() {
  size(340, 280, JAVA2D);
  strokeWeight(2);
  smooth();
  background(104);
  fill(200, 200, 200);
  noStroke();
  
  for (int i = 0; i < num_particles*2; i+=2) {
    particles[i] = random(2, screen_width-2);
    particles[i+1] = random(2, screen_height-2);
  }
  
  for (int i = 0; i < num_particles*2; i+=2) {
    vel[i] = random(-1,1);
    vel[i+1] = random(-1,1);
  }
}


void draw() {
 
  background(255);
  
  // update velocities
  for (int i = 0; i < num_particles*2; i+=2) {
    if (particles[i] + vel[i] > screen_width-2) {
      vel[i] *= -1;// + random(-10,10)/10;
    }
    else if (particles[i] + vel[i] < 2) {
      vel[i] *= -1;// + random(-10,10)/10;
    }
    
    if (particles[i+1] + vel[i+1] > screen_height-2) {
      vel[i+1] *= -1;// + random(-10,10)/10;
    }
    else if (particles[i+1] + vel[i+1] < 2) {
      vel[i+1] *= -1;// + random(-10,10)/10; 
    }
     
    if (vel[i] > 4) vel[i] = 4;
    else if (vel[i] < -4) vel[i] = -4;
    if (vel[i+1] > 4) vel[i+1] = 4;
    else if (vel[i+1] < -4) vel[i+1] = -4;
  }
  
  // update positions
  for (int i = 0; i < num_particles*2; i+=2) {
    particles[i] += vel[i];
    particles[i+1] += vel[i+1];
  }
  
  // draw
  for (int i = 0; i < num_particles*2; i+=2) {
    float z = sin(particles[i]/25) + sin(particles[i+1]/25);
    float disparity = z*4 + 4;
    fill(255,0,0,127);
    ellipse(particles[i], particles[i+1], 2, 2);
    fill(47,255,255,127);
    ellipse(particles[i]+disparity, particles[i+1], 2, 2);
    //ellipse(random(0,screen_width), random(0,screen_height), 200, 150);
    //rect(random(0,screen_width),random(0,screen_height),random(0,screen_width),random(0,screen_height));
  }
}



/*
% four_ambiguous_motion_cylinder

 

N = 100;           % number of dots
markersize = 2;  % size of dots
v = 0.04;           % velosity
nrep = 1000;        % number of repeat

pos = [522   160   875   816];
h = findobj('tag','rdot');
if isempty(h)
    figure('tag','rdot','color','k','doublebuffer','on','pos',pos)
end
r = 10;

% random dot
%x = cos(2*pi*rand(1,N));
y = rand(1,N)-0.25;
ymax = 0.75; %sqrt(1 - x.^2c);
dx_max = r*ymax*0.08;
theta0 = 2*pi*rand(1,N);
square_size = ymax * 0.1;
wx = [-1 -1 1 1]' * square_size;
wy = [-1 1 1 -1]' * square_size;
t = 0;
for i = 1:nrep
    t = t+v;
    Y = r*y;
    
    theta = theta0 + t;
    X = r*ymax.*cos(theta);

    dx = dx_max*(cos(theta-pi/2)+2);
    X_red = X + dx/2;
    %X_blue = X - dx/2;
    
    set(gca,'color','w')
    %alpha(0.5)
    % red squares
    %for n = 1:N
    %    area(X_red(n) + wx, Y(n) + wy,'FaceColor','r')
    %end
    Xr = repmat(X_red,size(wx,1),1)+repmat(wx,1,size(X_red,2));
    Yr = repmat(Y,size(wy,1),1)+repmat(wy,1,size(Y,2));
    fill(Xr,Yr,'r','FaceAlpha',0.5,'EdgeColor','none');
    
    hold on
    % blue squares
    %plot(X_blue,Y,'ob','MarkerFaceColor','b','Markersize',markersize);
    Xb = Xr-repmat(dx/2,size(wx,1),1);%repmat(X_blue,3,1)+repmat(wx',1,size(X_blue,2));
    Yb = Yr;%repmat(Y,3,1)+repmat(wy',1,size(Y,2));
    fill(Xb,Yb,[0.18 1 1],'FaceAlpha',0.5,'EdgeColor','none');
    
    %hold on
    %plot(X+r*2.5,Y,'ow','MarkerFaceColor','w','Markersize',markersize); hold on
    %plot(X+r*2.5,Y+r*2.5,'ow','MarkerFaceColor','w','Markersize',markersize); hold on
    %plot(X,Y+r*2.5,'ow','MarkerFaceColor','w','Markersize',markersize); hold on
    
    set(gca,'color','w')
    axis([-r r -r r])
    drawnow
    hold off
end
*/