shithub: boids

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implement boids algorithm.

--- a/main.c

+++ b/main.c

@@ -7,7 +7,8 @@

 #include <geometry.h>

 enum {

-	TERMINALV = 20

+	TERMINALV = 40,

+	BORDER = 100

 };

 enum {

@@ -22,6 +23,7 @@

 struct Bird

 {

 	Point2 p, v;

+	double sight;

 	Image *color;

 };

@@ -40,6 +42,7 @@

 RFrame worldrf;

 Image *pal[NCOLOR];

 Flock *flock;

+int nbirds;

 void flockseparate(Flock*);

 void flockalign(Flock*);

@@ -57,7 +60,7 @@

 		sysfatal("malloc: %r");

 	setmalloctag(f, getcallerpc(&nbirds));

 	f->birds = nil;

-	f->nbirds = 0;

+	f->nbirds = nbirds;

 	f->jail = jail;

 	f->separate = flockseparate;

 	f->align = flockalign;

@@ -64,34 +67,91 @@

 	f->cohesion = flockcohesion;

 	f->step = flockstep;

-	while(nbirds--){

-		f->birds = realloc(f->birds, ++f->nbirds*sizeof(Bird));

-		if(f->birds == nil)

-			sysfatal("realloc: %r");

-		b = &f->birds[f->nbirds-1];

-		b->p = Pt2(frand()*Dx(jail),frand()*Dy(jail),1);

+	f->birds = malloc(nbirds*sizeof(Bird));

+	if(f->birds == nil)

+		sysfatal("malloc: %r");

+	setmalloctag(f->birds, getcallerpc(&nbirds));

+	for(b = f->birds; b < f->birds + f->nbirds; b++){

+		b->p = Pt2(frand()*jail.max.x + jail.min.x,frand()*jail.max.y + jail.min.y,1);

 		b->v = Vec2(cos(frand()*2*PI),sin(frand()*2*PI));

 		b->v = mulpt2(b->v, TERMINALV);

+		b->sight = 75;

 		b->color = pal[Cfg];

 	}

-	setrealloctag(f->birds, getcallerpc(&nbirds));

 	return f;

 }

 void

-flockseparate(Flock *)

+flockseparate(Flock *f)

 {

+	static double comfortdist = 8;

+	static double repel = 0.05;

+	Point2 repelling, Δp;

+	Bird *b0, *b1;

+

+	for(b0 = f->birds; b0 < f->birds + f->nbirds; b0++){

+		repelling = Vec2(0,0);

+

+		for(b1 = f->birds; b1 < f->birds + f->nbirds; b1++)

+			if(b0 != b1){

+				Δp = subpt2(b0->p, b1->p);

+				if(vec2len(Δp) < comfortdist)

+					repelling = addpt2(repelling, Δp);

+			}

+

+		b0->v = addpt2(b0->v, mulpt2(repelling, repel));

+	}

 }

 void

-flockalign(Flock *)

+flockalign(Flock *f)

 {

+	static double attract = 0.05;

+	int neighbors;

+	Point2 attracting;

+	Bird *b0, *b1;

+

+	for(b0 = f->birds; b0 < f->birds + f->nbirds; b0++){

+		neighbors = 0;

+		attracting = Vec2(0,0);

+

+		for(b1 = f->birds; b1 < f->birds + f->nbirds; b1++)

+			if(vec2len(subpt2(b0->p, b1->p)) < b0->sight){

+				attracting = addpt2(attracting, b1->v);

+				neighbors++;

+			}

+

+		if(neighbors > 0){

+			attracting = divpt2(attracting, neighbors);

+			b0->v = addpt2(b0->v, mulpt2(subpt2(attracting, b0->v), attract));

+		}

+	}

 }

 void

-flockcohesion(Flock *)

+flockcohesion(Flock *f)

 {

+	static double center = 0.005;

+	int neighbors;

+	Point2 centering;

+	Bird *b0, *b1;

+

+	for(b0 = f->birds; b0 < f->birds + f->nbirds; b0++){

+		neighbors = 0;

+		centering = Vec2(0,0);

+

+		for(b1 = f->birds; b1 < f->birds + f->nbirds; b1++)

+			if(vec2len(subpt2(b0->p, b1->p)) < b0->sight){

+				centering = addpt2(centering, b1->p);

+				neighbors++;

+			}

+

+		if(neighbors > 0){

+			centering = divpt2(centering, neighbors);

+			b0->v = addpt2(b0->v, mulpt2(subpt2(centering, b0->p), center));

+		}

+	}

 }

 void

@@ -98,32 +158,31 @@

 flockstep(Flock *f)

 {

 	static double Δt = 1;

+	static Point2 a = {2,2}; /* deceleration */

 	Bird *b;

-	//f->separate(f);

-	//f->align(f);

-	//f->cohesion(f);

+	f->separate(f);

+	f->align(f);

+	f->cohesion(f);

 	for(b = f->birds; b < f->birds + f->nbirds; b++){

 		b->p = addpt2(b->p, mulpt2(b->v, Δt));

-		if(b->p.x < 0){

-			b->p.x = 0;

-			b->v.x = -b->v.x;

-		}

-		if(b->p.y < 0){

-			b->p.y = 0;

-			b->v.y = -b->v.y;

-		}

-		if(b->p.x > Dx(f->jail)){

-			b->p.x = Dx(f->jail);

-			b->v.x = -b->v.x;

-		}

-		if(b->p.y > Dy(f->jail)){

-			b->p.y = Dy(f->jail);

-			b->v.y = -b->v.y;

-		}

+		if(b->p.x < f->jail.min.x)

+			b->v.x += a.x;

+		if(b->p.y < f->jail.min.y)

+			b->v.y += a.y;

+		if(b->p.x > f->jail.max.x)

+			b->v.x -= a.x;

+		if(b->p.y > f->jail.max.y)

+			b->v.y -= a.y;

 	}

 }

+void

+resetflock(void)

+{

+	flock = newflock(nbirds, Rect(BORDER,BORDER,Dx(screen->r)-BORDER,Dy(screen->r)-BORDER));

+}

+

 Point

 toscreen(Point2 p)

 {

@@ -151,9 +210,8 @@

 	lockdisplay(display);

 	draw(screen, screen->r, pal[Cbg], nil, ZP);

-	for(b = flock->birds; b < flock->birds + flock->nbirds; b++){

+	for(b = flock->birds; b < flock->birds + flock->nbirds; b++)

 		ellipse(screen, toscreen(b->p), 2, 2, 0, b->color, ZP);

-	}

 	flushimage(display, 1);

 	unlockdisplay(display);

 }

@@ -166,16 +224,45 @@

 		sysfatal("resize failed");

 	unlockdisplay(display);

 	worldrf.p = Pt2(screen->r.min.x,screen->r.max.y,1);

-	flock->jail = Rect(0,0,Dx(screen->r),Dy(screen->r));

+	flock->jail = Rect(BORDER,BORDER,Dx(screen->r)-BORDER,Dy(screen->r)-BORDER);

 	redraw();

 }

 void

-mouse(Mouse)

+rmb(Mousectl *mc, Keyboardctl *kc)

 {

+	enum {

+		RESET,

+		NBIRDS

+	};

+	static char *items[] = {

+	 [RESET]	"reset",

+	 [NBIRDS]	"set bird number",

+		nil

+	};

+	static Menu menu = { .item = items };

+	char buf[128];

+

+	switch(menuhit(3, mc, &menu, nil)){

+	case NBIRDS:

+		snprint(buf, sizeof buf, "%d", nbirds);

+		enter("nbirds", buf, sizeof buf, mc, kc, nil);

+		nbirds = strtol(buf, nil, 10);

+	case RESET:

+		srand(time(nil));

+		resetflock();

+		break;

+	}

 }

 void

+mouse(Mousectl *mc, Keyboardctl *kc)

+{

+	if((mc->buttons&4) != 0)

+		rmb(mc, kc);

+}

+

+void

 key(Rune r)

 {

 	switch(r){

@@ -202,9 +289,8 @@

 	Keyboardctl *kc;

 	Rune r;

 	char *s;

-	int nbirds;

-	nbirds = 10;

+	nbirds = 100;

 	ARGBEGIN{

 	case 'n':

 		nbirds = strtol(EARGF(usage()), &s, 10);

@@ -226,9 +312,8 @@

 	worldrf.p = Pt2(screen->r.min.x,screen->r.max.y,1);

 	worldrf.bx = Vec2(1, 0);

 	worldrf.by = Vec2(0,-1);

+	resetflock();

-	flock = newflock(nbirds, Rect(0,0,Dx(screen->r),Dy(screen->r)));

-

 	display->locking = 1;

 	unlockdisplay(display);

 	redraw();

@@ -244,7 +329,7 @@

 		switch(alt(a)){

 		case MOUSE:

-			mouse(mc->Mouse);

+			mouse(mc, kc);

 			break;

 		case RESIZE:

 			resized();