// Smoke 
// by Glen Murphy <http://www.bodytag.org> 

int res = 2; 
int penSize = 30; 
int lwidth; 
int lheight; 
int pnum = 30000; 
vsquare[][] v; 
vbuffer[][] vbuf; 
particle[] p; 
int pcount = 0; 
int mouseXvel = 0; 
int mouseYvel = 0; 
 
int randomGust = 0; 
int randomGustMax; 
float randomGustX; 
float randomGustY; 
float randomGustSize; 
float randomGustXvel; 
float randomGustYvel; 
 
void setup() 
{ 
  size(200, 200); 
  lwidth = width/res; 
  lheight = height/res; 
  v = new vsquare[lwidth+1][lheight+1]; 
  vbuf = new vbuffer[lwidth+1][lheight+1]; 
  p = new particle[pnum]; 
  noStroke(); 
  framerate(60); 
  for(int i = 0; i < pnum; i++) { 
    p[i] = new particle(random(width/2-20,width/2+20),random(height-20,height)); 
  } 
  for(int i = 0; i <= lwidth; i++) { 
    for(int u = 0; u <= lheight; u++) { 
      v[i][u] = new vsquare(i*res,u*res); 
      vbuf[i][u] = new vbuffer(i*res,u*res); 
    } 
  } 
} 
 
void draw() 
{ 
  background(#cccccc); 
  
  int axvel = mouseX-pmouseX; 
  int ayvel = mouseY-pmouseY; 
 
  mouseXvel = (axvel != mouseXvel) ? axvel : 0; 
  mouseYvel = (ayvel != mouseYvel) ? ayvel : 0; 
 
  if(randomGust <= 0) { 
    if(random(0,10)<1) { 
      randomGustMax = (int)random(5,12); 
      randomGust = randomGustMax; 
      randomGustX = random(0,width); 
      randomGustY = random(0,height-10); 
      randomGustSize = random(0,50); 
      if(randomGustX > width/2) { 
        randomGustXvel = random(-8,0); 
      } else { 
        randomGustXvel = random(0,8); 
      } 
      randomGustYvel = random(-2,1); 
    } 
    randomGust--; 
  } 
 
  for(int i = 0; i < lwidth; i++) { 
    for(int u = 0; u < lheight; u++) { 
      vbuf[i][u].updatebuf(i,u); 
      v[i][u].col = 0; 
    } 
  } 
  for(int i = 0; i < pnum-1; i++) { 
    p[i].updatepos(); 
  } 
  for(int i = 0; i < lwidth; i++) { 
    for(int u = 0; u < lheight; u++) { 
      v[i][u].addbuffer(i, u); 
      v[i][u].updatevels(mouseXvel, mouseYvel); 
      v[i][u].display(i, u); 
    } 
  } 
  randomGust = 0; 
} 
 
class particle 
{ 
  float x; 
  float y; 
  float xvel; 
  float yvel; 
  float temp; 
  int pos; 
 
  particle(float xIn, float yIn) { 
    x = xIn; 
    y = yIn; 
  } 
 
  void reposition() { 
    x = width/2+random(-20,20); 
    y = random(height-10,height); 
 
    xvel = random(-1,1); 
    yvel = random(-1,1); 
  } 
 
  void updatepos() { 
    int vi = (int)(x/res); 
    int vu = (int)(y/res); 
 
    if(vi > 0 && vi < lwidth && vu > 0 && vu < lheight) { 
      v[vi][vu].addcolour(2); 
 
      float ax = (x%res)/res; 
      float ay = (y%res)/res; 
 
      xvel += (1-ax)*v[vi][vu].xvel*0.05; 
      yvel += (1-ay)*v[vi][vu].yvel*0.05; 
 
      xvel += ax*v[vi+1][vu].xvel*0.05; 
      yvel += ax*v[vi+1][vu].yvel*0.05; 
 
      xvel += ay*v[vi][vu+1].xvel*0.05; 
      yvel += ay*v[vi][vu+1].yvel*0.05; 
 
      v[vi][vu].yvel -= (1-ay)*0.003; 
      v[vi+1][vu].yvel -= ax*0.003; 
 
      if(v[vi][vu].yvel < 0) v[vi][vu].yvel *= 1.00025; 
 
      x += xvel; 
      y += yvel; 
    } 
    else { 
      reposition(); 
    } 
    if(random(0,400) < 1) { 
      reposition(); 
    } 
    xvel *= 0.6; 
    yvel *= 0.6; 
  } 
} 
 
class vbuffer 
{ 
  int x; 
  int y; 
  float xvel; 
  float yvel; 
  float pressurex = 0; 
  float pressurey = 0; 
  float pressure = 0; 
 
  vbuffer(int xIn,int yIn) { 
    x = xIn; 
    y = yIn; 
    pressurex = 0; 
    pressurey = 0; 
  } 
 
  void updatebuf(int i, int u) { 
    if(i>0 && i<lwidth && u>0 && u<lheight) { 
      pressurex = (v[i-1][u-1].xvel*0.5 + v[i-1][u].xvel + v[i-1][u+1].xvel*0.5 - v[i+1][u-1].xvel*0.5 - v[i+1][u].xvel - v[i+1][u+1].xvel*0.5); 
      pressurey = (v[i-1][u-1].yvel*0.5 + v[i][u-1].yvel + v[i+1][u-1].yvel*0.5 - v[i-1][u+1].yvel*0.5 - v[i][u+1].yvel - v[i+1][u+1].yvel*0.5); 
      pressure = (pressurex + pressurey)*0.25; 
    } 
  } 
} 
 
class vsquare { 
  int x; 
  int y; 
  float xvel; 
  float yvel; 
  float col; 
 
  vsquare(int xIn,int yIn) { 
    x = xIn; 
    y = yIn; 
  } 
 
  void addbuffer(int i, int u) { 
    if(i>0 && i<lwidth && u>0 && u<lheight) { 
      xvel += (vbuf[i-1][u-1].pressure*0.5 
      +vbuf[i-1][u].pressure 
      +vbuf[i-1][u+1].pressure*0.5 
      -vbuf[i+1][u-1].pressure*0.5 
      -vbuf[i+1][u].pressure 
      -vbuf[i+1][u+1].pressure*0.5 
      )*0.49; 
      yvel += (vbuf[i-1][u-1].pressure*0.5 
      +vbuf[i][u-1].pressure 
      +vbuf[i+1][u-1].pressure*0.5 
      -vbuf[i-1][u+1].pressure*0.5 
      -vbuf[i][u+1].pressure 
      -vbuf[i+1][u+1].pressure*0.5 
      )*0.49; 
    } 
  } 
 
  void updatevels(int mvelX, int mvelY) { 
    float adj; 
    float opp; 
    float dist; 
    float mod; 
 
    if(mousePressed) { 
      adj = x - mouseX; 
      opp = y - mouseY; 
      dist = sqrt(opp*opp + adj*adj); 
      if(dist < penSize) { 
        if(dist < 4) dist = penSize; 
        mod = penSize/dist; 
        xvel += mvelX*mod; 
        yvel += mvelY*mod; 
      } 
    } 
    if(randomGust > 0) { 
      adj = x - randomGustX; 
      opp = y - randomGustY; 
      dist = sqrt(opp*opp + adj*adj); 
      if(dist < randomGustSize) { 
        if(dist < res*2) dist = randomGustSize; 
        mod = randomGustSize/dist; 
        xvel += (randomGustMax-randomGust)*randomGustXvel*mod; 
        yvel += (randomGustMax-randomGust)*randomGustYvel*mod; 
      } 
    } 
    xvel *= 0.99; 
    yvel *= 0.98; 
  } 
 
  void addcolour(int amt) { 
    col += amt; 
    if(col > 196) col = 196; 
  } 
 
  void display(int i, int u) { 
    float tcol = 0; 
    if(i>0 && i<lwidth-1 && u>0 && u<lheight-1) { 
 
      tcol = (+ v[i][u+1].col 
      + v[i+1][u].col 
      + v[i+1][u+1].col*0.5 
      )*0.3; 
      tcol = (int)(tcol+col*0.5); 
    } 
 
    fill(255-tcol, 255-tcol, 255-tcol); 
    rect(x,y,res,res); 
    col = 0; 
  } 
}