Import sources from 2011-03-30 iso image

1 files changed, 190 insertions, 0 deletions

diff --git a/sys/src/cmd/astro/occ.c b/sys/src/cmd/astro/occ.c
new file mode 100755
index 000000000..c0c8bc841
--- /dev/null
+++ b/sys/src/cmd/astro/occ.c
@@ -0,0 +1,190 @@
+#include "astro.h"
+
+Occ	 o1, o2;
+Obj2	 xo1, xo2;
+
+void
+occult(Obj2 *p1, Obj2 *p2, double)
+{
+	int i, i1, N;
+	double d1, d2, d3, d4;
+	double x, di, dx, x1;
+
+	d3 = 0;
+	d2 = 0;
+	occ.t1 = -100;
+	occ.t2 = -100;
+	occ.t3 = -100;
+	occ.t4 = -100;
+	occ.t5 = -100;
+	for(i=0; i<=NPTS+1; i++) {
+		d1 = d2;
+		d2 = d3;
+		d3 = dist(&p1->point[i], &p2->point[i]);
+		if(i >= 2 && d2 <= d1 && d2 <= d3)
+			goto found;
+	}
+	return;
+
+found:
+	N = 2880*PER/NPTS; /* 1 min steps */
+	i -= 2;
+	set3pt(p1, i, &o1);
+	set3pt(p2, i, &o2);
+
+	di = i;
+	x = 0;
+	dx = 2./N;
+	for(i=0; i<=N; i++) {
+		setpt(&o1, x);
+		setpt(&o2, x);
+		d1 = d2;
+		d2 = d3;
+		d3 = dist(&o1.act, &o2.act);
+		if(i >= 2 && d2 <= d1 && d2 <= d3)
+			goto found1;
+		x += dx;
+	}
+	fprint(2, "bad 1 \n");
+	return;
+
+found1:
+	if(d2 > o1.act.semi2+o2.act.semi2+50)
+		return;
+	di += x - 3*dx;
+	x = 0;
+	for(i=0; i<3; i++) {
+		setime(day + deld*(di + x));
+		(*p1->obj)();
+		setobj(&xo1.point[i]);
+		(*p2->obj)();
+		setobj(&xo2.point[i]);
+		x += 2*dx;
+	}
+	dx /= 60;
+	x = 0;
+	set3pt(&xo1, 0, &o1);
+	set3pt(&xo2, 0, &o2);
+	for(i=0; i<=240; i++) {
+		setpt(&o1, x);
+		setpt(&o2, x);
+		d1 = d2;
+		d2 = d3;
+		d3 = dist(&o1.act, &o2.act);
+		if(i >= 2 && d2 <= d1 && d2 <= d3)
+			goto found2;
+		x += 1./120.;
+	}
+	fprint(2, "bad 2 \n");
+	return;
+
+found2:
+	if(d2 > o1.act.semi2 + o2.act.semi2)
+		return;
+	i1 = i-1;
+	x1 = x - 1./120.;
+	occ.t3 = di + i1 * dx;
+	occ.e3 = o1.act.el;
+	d3 = o1.act.semi2 - o2.act.semi2;
+	if(d3 < 0)
+		d3 = -d3;
+	d4 = o1.act.semi2 + o2.act.semi2;
+	for(i=i1,x=x1;; i++) {
+		setpt(&o1, x);
+		setpt(&o2, x);
+		d1 = d2;
+		d2 = dist(&o1.act, &o2.act);
+		if(i != i1) {
+			if(d1 <= d3 && d2 > d3) {
+				occ.t4 = di + (i-.5) * dx;
+				occ.e4 = o1.act.el;
+			}
+			if(d2 > d4) {
+				if(d1 <= d4) {
+					occ.t5 = di + (i-.5) * dx;
+					occ.e5 = o1.act.el;
+				}
+				break;
+			}
+		}
+		x += 1./120.;
+	}
+	for(i=i1,x=x1;; i--) {
+		setpt(&o1, x);
+		setpt(&o2, x);
+		d1 = d2;
+		d2 = dist(&o1.act, &o2.act);
+		if(i != i1) {
+			if(d1 <= d3 && d2 > d3) {
+				occ.t2 = di + (i+.5) * dx;
+				occ.e2 = o1.act.el;
+			}
+			if(d2 > d4) {
+				if(d1 <= d4) {
+					occ.t1 = di + (i+.5) * dx;
+					occ.e1 = o1.act.el;
+				}
+				break;
+			}
+		}
+		x -= 1./120.;
+	}
+}
+
+void
+setpt(Occ *o, double x)
+{
+	double y;
+
+	y = x * (x-1);
+	o->act.ra = o->del0.ra +
+		x*o->del1.ra + y*o->del2.ra;
+	o->act.decl2 = o->del0.decl2 +
+		x*o->del1.decl2 + y*o->del2.decl2;
+	o->act.semi2 = o->del0.semi2 +
+		x*o->del1.semi2 + y*o->del2.semi2;
+	o->act.el = o->del0.el +
+		x*o->del1.el + y*o->del2.el;
+}
+
+
+double
+pinorm(double a)
+{
+
+	while(a < -pi)
+		a += pipi;
+	while(a > pi)
+		a -= pipi;
+	return a;
+}
+
+void
+set3pt(Obj2 *p, int i, Occ *o)
+{
+	Obj1 *p1, *p2, *p3;
+	double a;
+
+	p1 = p->point+i;
+	p2 = p1+1;
+	p3 = p2+1;
+
+	o->del0.ra = p1->ra;
+	o->del0.decl2 = p1->decl2;
+	o->del0.semi2 = p1->semi2;
+	o->del0.el = p1->el;
+
+	a = p2->ra - p1->ra;
+	o->del1.ra = pinorm(a);
+	a = p2->decl2 - p1->decl2;
+	o->del1.decl2 = pinorm(a);
+	o->del1.semi2 = p2->semi2 - p1->semi2;
+	o->del1.el = p2->el - p1->el;
+
+	a = p1->ra + p3->ra - 2*p2->ra;
+	o->del2.ra = pinorm(a)/2;
+	a = p1->decl2 + p3->decl2 - 2*p2->decl2;
+	o->del2.decl2 = pinorm(a)/2;
+	o->del2.semi2 = (p1->semi2 + p3->semi2 - 2*p2->semi2) / 2;
+	o->del2.el = (p1->el + p3->el - 2*p2->el) / 2;
+}