initial commit. first stages of simulation, per-second steps avoiding the jail bars.

4 files changed, 292 insertions, 0 deletions

diff --git a/main.c b/main.c
new file mode 100644
index 0000000..a9c33cb
--- /dev/null
+++ b/main.c
@@ -0,0 +1,259 @@
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+#include <draw.h>
+#include <mouse.h>
+#include <keyboard.h>
+#include <geometry.h>
+
+enum {
+	TERMINALV = 20
+};
+
+enum {
+	Cbg,
+	Cfg,
+	NCOLOR
+};
+
+typedef struct Bird Bird;
+typedef struct Flock Flock;
+
+struct Bird
+{
+	Point2 p, v;
+	Image *color;
+};
+
+struct Flock
+{
+	Bird *birds;
+	int nbirds;
+	Rectangle jail;
+
+	void (*separate)(Flock*);
+	void (*align)(Flock*);
+	void (*cohesion)(Flock*);
+	void (*step)(Flock*);
+};
+
+RFrame worldrf;
+Image *pal[NCOLOR];
+Flock *flock;
+
+void flockseparate(Flock*);
+void flockalign(Flock*);
+void flockcohesion(Flock*);
+void flockstep(Flock*);
+
+Flock*
+newflock(int nbirds, Rectangle jail)
+{
+	Flock *f;
+	Bird *b;
+
+	f = malloc(sizeof(Flock));
+	if(f == nil)
+		sysfatal("malloc: %r");
+	setmalloctag(f, getcallerpc(&nbirds));
+	f->birds = nil;
+	f->nbirds = 0;
+	f->jail = jail;
+	f->separate = flockseparate;
+	f->align = flockalign;
+	f->cohesion = flockcohesion;
+	f->step = flockstep;
+
+	while(nbirds--){
+		f->birds = realloc(f->birds, ++f->nbirds*sizeof(Bird));
+		if(f->birds == nil)
+			sysfatal("realloc: %r");
+		setrealloctag(f->birds, getcallerpc(&nbirds));
+		b = &f->birds[f->nbirds-1];
+		b->p = Pt2(frand()*Dx(jail),frand()*Dy(jail),1);
+		b->v = Vec2(cos(frand()*2*PI),sin(frand()*2*PI));
+		b->v = mulpt2(b->v, TERMINALV);
+		b->color = pal[Cfg];
+	}
+
+	return f;
+}
+
+void
+flockseparate(Flock *)
+{
+}
+
+void
+flockalign(Flock *)
+{
+}
+
+void
+flockcohesion(Flock *)
+{
+}
+
+void
+flockstep(Flock *f)
+{
+	static double Δt = 1;
+	Bird *b;
+
+	//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;
+		}
+	}
+}
+
+Point
+toscreen(Point2 p)
+{
+	p = invrframexform(p, worldrf);
+	return Pt(p.x,p.y);
+}
+
+Point2
+fromscreen(Point p)
+{
+	return rframexform(Pt2(p.x,p.y,1), worldrf);
+}
+
+void
+initpalette(void)
+{
+	pal[Cbg] = allocimage(display, Rect(0,0,1,1), screen->chan, 1, 0x000000ff);
+	pal[Cfg] = allocimage(display, Rect(0,0,1,1), screen->chan, 1, 0xffffffff);
+}
+
+void
+redraw(void)
+{
+	Bird *b;
+
+	lockdisplay(display);
+	draw(screen, screen->r, pal[Cbg], nil, ZP);
+	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);
+}
+
+void
+resized(void)
+{
+	lockdisplay(display);
+	if(getwindow(display, Refnone) < 0)
+		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));
+	redraw();
+}
+
+void
+mouse(Mouse)
+{
+}
+
+void
+key(Rune r)
+{
+	switch(r){
+	case Kdel:
+	case 'q':
+		threadexitsall(nil);
+	case ' ':
+		flock->step(flock);
+		break;
+	}
+}
+
+void
+usage(void)
+{
+	fprint(2, "usage: %s [-n nbirds]\n", argv0);
+	exits("usage");
+}
+
+void
+threadmain(int argc, char *argv[])
+{
+	Mousectl *mc;
+	Keyboardctl *kc;
+	Rune r;
+	char *s;
+	int nbirds;
+
+	nbirds = 10;
+	ARGBEGIN{
+	case 'n':
+		nbirds = strtol(EARGF(usage()), &s, 10);
+		if(*s != 0)
+			usage();
+		break;
+	default: usage();
+	}ARGEND;
+	if(argc > 0)
+		usage();
+
+	if(initdraw(nil, nil, nil) < 0)
+		sysfatal("initdraw: %r");
+	if((mc = initmouse(nil, screen)) == nil)
+		sysfatal("initmouse: %r");
+	if((kc = initkeyboard(nil)) == nil)
+		sysfatal("initkeyboard: %r");
+	initpalette();
+	worldrf.p = Pt2(screen->r.min.x,screen->r.max.y,1);
+	worldrf.bx = Vec2(1, 0);
+	worldrf.by = Vec2(0,-1);
+
+	flock = newflock(nbirds, Rect(0,0,Dx(screen->r),Dy(screen->r)));
+
+	display->locking = 1;
+	unlockdisplay(display);
+	redraw();
+
+	for(;;){
+		enum { MOUSE, RESIZE, KEYBOARD };
+		Alt a[] = {
+			{mc->c, &mc->Mouse, CHANRCV},
+			{mc->resizec, nil, CHANRCV},
+			{kc->c, &r, CHANRCV},
+			{nil, nil, CHANEND}
+		};
+
+		switch(alt(a)){
+		case MOUSE:
+			mouse(mc->Mouse);
+			break;
+		case RESIZE:
+			resized();
+			break;
+		case KEYBOARD:
+			key(r);
+			break;
+		}
+
+		redraw();
+	}
+}
diff --git a/mkfile b/mkfile
new file mode 100644
index 0000000..ecdffae
--- /dev/null
+++ b/mkfile
@@ -0,0 +1,24 @@
+</$objtype/mkfile
+
+BIN=/$objtype/bin/games
+TARG=boids
+OFILES=\
+	main.$O\
+
+HFILES=\
+	libgeometry/geometry.h\
+
+LIB=\
+	libgeometry/libgeometry.a$O\
+
+CFLAGS=$CFLAGS -Ilibgeometry
+
+</sys/src/cmd/mkone
+
+libgeometry/libgeometry.a$O:
+	cd libgeometry
+	mk install
+
+clean nuke:V:
+	rm -f *.[$OS] [$OS].??* $TARG
+	@{cd libgeometry; mk $target}
diff --git a/readme.md b/readme.md
new file mode 100644
index 0000000..89cb4fd
--- /dev/null
+++ b/readme.md
@@ -0,0 +1,6 @@
+# Bird flock simulator
+
+This program shows the emergent behavior observed in bird flocks,
+mammal herds, fish schools and other such animal groups.  It's based
+on Craig W. Reynolds' “Flocks, Herds and Schools: A Distributed
+Behavioral Model.”
diff --git a/resources b/resources
new file mode 100644
index 0000000..63deb84
--- /dev/null
+++ b/resources
@@ -0,0 +1,3 @@
+http://www.red3d.com/cwr/boids/
+http://www.red3d.com/cwr/papers/1987/boids.html
+http://www.red3d.com/cwr/boids/RipOff_Flocking.html