Forest fire: Difference between revisions

=={{header|Evaldraw}}==

[[File:Evaldrawforest.gif|right|thumb|Forest fire animation]]

Creates a 256x256 pixel forest, try adjusting the probability for ignite, spread, sprout and max neighbors.

<syntaxhighlight lang="c">

enum{XSIZ=255, YSIZ=XSIZ} // size of forest

enum{EMPTY=0, TREE=1, BURN=2} // possible states of a cell

static prob_ignite = .000001; // very rare, but remember we have many trees.

static prob_spread = .25; // Fire spread speed/probability if neighbor on fire

static prob_sprout = 0.25; // probability of new tree to sprout

static MAX_NEIGHBORS = 6; // tree refuses to sprout if overcrowded

static forest[2][YSIZ][XSIZ]; // state of pixel

static fuel[2][YSIZ][XSIZ]; // stores fuel (wood) 0-255

static heat[2][YSIZ][XSIZ]; // tree refuses to spout if heat!=0, also, sets draw color.

static arr_numburn[YSIZ][XSIZ]; // number of burning trees for this cell

static arr_numtree[YSIZ][XSIZ]; // number of neighbor trees for this cell

static xoff[8] = {-1,+0,+1,-1,/*NA*/1,-1,+0,+1}; // offsets to find 8-connected neighbors

static yoff[8] = {-1,-1,-1,+0,/*NA*/0,+1,+1,+1};

() { // Main in evaldraw scripts is a unnamed function.

static otim;

tim = klock(); // Time since program start in seconds.

dt=tim-otim; // Deltatime. 1/dt is FPS. 0 in first frame.

otim=tim; // store old time for next dt.

simulate(); // simulate and draw are coupled, since draw also ping-pongs state.

draw();

setcol(0); fillrect(0,YSIZ,XSIZ,15);

setcol(0xffffff); moveto(0,YSIZ); printf("%4.0ffps generation %5.0f", 1 /dt, numframes);

if (bstatus>0) setFire(mousx,mousy);

}// end main

draw() {

for(y=0; y<YSIZ; y++)

for(x=0; x<XSIZ; x++)

{

cell = forest[1][y][x];

if (cell == EMPTY) setcol(0);

else if(cell==BURN) setcol(511-.25*fuel[0][y][x],255-3*heat[0][y][x],33);

else if(cell==TREE) setcol(0,64+fuel[0][y][x],0);

setpix(x,y);

// Transfer next simulation state into current ready for next frame

forest[0][y][x] = forest[1][y][x];

heat[0][y][x] = heat[1][y][x];

fuel[0][y][x] = fuel[1][y][x];

// Count neighbors burning and not

numburn = 0; numtree = 0;

for(n=0; n<8; n++) {

ypos=y+yoff[n];

xpos=x+xoff[n];

if (xpos<0 || xpos > XSIZ-1)continue;

if (ypos<0 || ypos > YSIZ-1)continue;

cell = forest[1][ypos][xpos];

if (cell==BURN) numburn++;

else if (cell==TREE) numtree++;

}

arr_numburn[y][x] = numburn;

arr_numtree[y][x] = numtree;

}

}

fillrect(x0,y0,w,h) {

x0=int(x0); y0=int(y0); w=int(w) + 1; h=int(h);

for(y=y0;y<=y0+h;y++) { moveto(x0,y); lineto(x0+w,y); }

}

simulate() {

for(y=0; y<YSIZ; y++)

for(x=0; x<XSIZ; x++) {

cell = forest[0][y][x];

cellfuel = fuel[0][y][x];

celltemp = heat[0][y][x];

rand=rnd;

numburn = arr_numburn[y][x];

numtree = arr_numtree[y][x];

if (cell == BURN) {

if (cellfuel <= 0) {

forest[1][y][x] = EMPTY;

}

else {

fuel[1][y][x] = cellfuel - 1;

heat[1][y][x] = celltemp + 1;

}

}

else if (cell == TREE) {

if (numburn == 0 && rand < prob_ignite) setFire(x,y);

else if (numburn > 0 && rand < prob_spread) setFire(x,y);

else if(cellfuel < 255) fuel[1][y][x] = cellfuel + 1;

}

else if (cell == EMPTY) {

if ( celltemp > 0 ) heat[1][y][x] = celltemp - 1;

else if (numburn==0 && rand < prob_sprout && numtree <= MAX_NEIGHBORS) setTree(x,y);

}

}

} // end sim

setFire(x,y) {

forest[1][y][x] = BURN;

}

setTree(x,y) {

forest[1][y][x] = TREE;

}

</syntaxhighlight>