diffusion

gistfile1.txt

int w=500;
int h=500;

float[][] aVal = new float[w][h];
float[][] bVal =  new float[w][h];
float[][] newA = new float[w][h];
float[][] newB = new float[w][h];

float[] lapA = new float[w*h];
float[] lapB = new float[w*h];
float diffusionA, diffusionB;
float reactionRateA, reactionRateB;
float replenishmentA, replenishmentB;
float diffusionRateA = 1.0;
float diffusionRateB = .5;
float feedRate = .0545;
float killRate = .062;
float time = .2;


void setup() {
  size(w, h);
  for (int x=0; x < w; x++) {
    for (int y=0; y < h; y++) {
//      println("x: " + x );
//      println("y: " + y);
      aVal[x][y] = 1.0;
      bVal[x][y] = 0.0;
      }
  }
}
void draw() {
  background(0);
  laplace();
  update();
  loadPixels();
  for (int x=0;x<w;x++) {
    for (int y=0;y<h;y++) {
      pixels[x+y*w] = color(newA[x][y]*255);
    }
  }
  updatePixels();

}


void update(){
//laplace();
for (int x = 0; x < w; x++) {
  for (int y = 0; y < h; y++) {
diffusionA = diffusionRateA*lapA[x+y*w];
diffusionB = diffusionRateB*lapB[x+y*w];
reactionRateA = -aVal[x][y]*bVal[x][y]*bVal[x][y];
reactionRateB = aVal[x][y]*bVal[x][y]*bVal[x][y];
replenishmentA = feedRate*(1-aVal[x][y]);
replenishmentB = -(killRate+feedRate)*bVal[x][y];
newA[x][y] = aVal[x][y] +(diffusionA +reactionRateA + replenishmentA)*time;
newB[x][y] = bVal[x][y] +(diffusionB +reactionRateB + replenishmentB)*time;
  }}
}

void laplace(){

for (int x = 1; x < w-1; x++) {
  for (int y = 1; y < h-1; y++) {
    float templapA =
      aVal[x][y+1] * .2+
      aVal[x][y-1]* .2+
      aVal[x+1][y]* .2+
      aVal[x-1][y]* .2+
      aVal[x+1][y+1]* .05+
      aVal[x-1][y+1]* .05+
      aVal[x+1][y-1]* .05+
      aVal[x-1][y-1]* .05+
      aVal[x][y]* -1.0;
    lapA[x+y*width] = templapA;
    float templapB =
      bVal[x][y+1] * .2+
      bVal[x][y-1]* .2+
      bVal[x+1][y]* .2+
      bVal[x-1][y]* .2+
      bVal[x+1][y+1]* .05+
      bVal[x-1][y+1]* .05+
      bVal[x+1][y-1]* .05+
      bVal[x-1][y-1]* .05+
      bVal[x][y]* -1.0;
    lapB[x+y*width] = templapB;
  }
}
}

void mousePressed(){
  for ( int x= mouseX-20; x<mouseX+20; x++){
    for (int y=mouseY -20; y<mouseY+20; y++){
      if (random(1.0)>.5){
      bVal[x][y] = 1.0;
      }
    }}
    
}