| 1 |
/* Copyright (c) 1991 Regents of the University of California */ |
| 2 |
|
| 3 |
#ifndef lint |
| 4 |
static char SCCSid[] = "$SunId$ LBL"; |
| 5 |
#endif |
| 6 |
|
| 7 |
/* |
| 8 |
* Generate an N-dimensional Peano space-filling curve |
| 9 |
* on the interval [0,1). |
| 10 |
* |
| 11 |
* 12 Aug 91 Greg Ward |
| 12 |
*/ |
| 13 |
|
| 14 |
extern double floor(); |
| 15 |
|
| 16 |
|
| 17 |
static double |
| 18 |
peanoC(n, t, e) /* compute Peano coordinate */ |
| 19 |
int n; |
| 20 |
double t, e; |
| 21 |
{ |
| 22 |
register int i; |
| 23 |
double d; |
| 24 |
|
| 25 |
if (e >= 1./3.) |
| 26 |
return(t); |
| 27 |
d = 0.; |
| 28 |
while (t-d >= 1./3.) |
| 29 |
d += 1./3.; |
| 30 |
i = n; |
| 31 |
while (--i > 0) |
| 32 |
t *= 3.; |
| 33 |
t = 3.*(t - floor(t)); |
| 34 |
i = 0; |
| 35 |
while (t >= 1.) { |
| 36 |
t -= 1.; |
| 37 |
i ^= 1; |
| 38 |
} |
| 39 |
t = peanoC(n, t, 3.*e); |
| 40 |
if (i) |
| 41 |
t = 1. - t; |
| 42 |
return(d + t/3.); |
| 43 |
} |
| 44 |
|
| 45 |
|
| 46 |
peano(p, n, t, e) /* compute Peano point */ |
| 47 |
register double p[]; |
| 48 |
int n; |
| 49 |
double t, e; |
| 50 |
{ |
| 51 |
register int i; |
| 52 |
register int neg = 0; |
| 53 |
|
| 54 |
i = n; |
| 55 |
while (i-- > 0) { |
| 56 |
p[i] = peanoC(n, t, e); |
| 57 |
if (neg) |
| 58 |
p[i] = 1. - p[i]; |
| 59 |
t *= 3.; |
| 60 |
while (t >= 1.) { |
| 61 |
t -= 1.; |
| 62 |
neg ^= 1; |
| 63 |
} |
| 64 |
} |
| 65 |
} |
