1 |
#ifndef lint |
2 |
static const char RCSid[] = "$Id: hermite3.c,v 2.3 2003/06/08 12:03:09 schorsch Exp $"; |
3 |
#endif |
4 |
/* |
5 |
* hermite.c - routines for 3D hermite curves. |
6 |
* |
7 |
* 10/29/85 |
8 |
*/ |
9 |
|
10 |
#include <stdio.h> |
11 |
|
12 |
void |
13 |
hermite3( /* compute point on hermite curve */ |
14 |
double hp[3], /* returned hermite point */ |
15 |
double p0[3], /* first endpoint */ |
16 |
double p1[3], /* second endpoint */ |
17 |
double r0[3], /* tangent at p0 */ |
18 |
double r1[3], /* tangent at p1 */ |
19 |
double t /* position parameter */ |
20 |
) |
21 |
{ |
22 |
register int i; |
23 |
double tmh[4]; |
24 |
|
25 |
tmh[0] = (2.0*t - 3.0)*t*t + 1.0; |
26 |
tmh[1] = (-2.0*t + 3.0)*t*t; |
27 |
tmh[2] = ((t - 2.0)*t + 1.0)*t; |
28 |
tmh[3] = (t - 1.0)*t*t; |
29 |
|
30 |
for (i = 0; i < 3; i++) |
31 |
hp[i] = p0[i]*tmh[0] + p1[i]*tmh[1] + |
32 |
r0[i]*tmh[2] + r1[i]*tmh[3]; |
33 |
} |
34 |
|
35 |
|
36 |
void |
37 |
htan3( /* compute tangent on hermite curve */ |
38 |
double ht[3], /* returned hermite tangent */ |
39 |
double p0[3], /* first endpoint */ |
40 |
double p1[3], /* second endpoint */ |
41 |
double r0[3], /* tangent at p0 */ |
42 |
double r1[3], /* tangent at p1 */ |
43 |
double t /* position parameter */ |
44 |
) |
45 |
{ |
46 |
register int i; |
47 |
double tpmh[4]; |
48 |
|
49 |
tpmh[0] = (6.0*t - 6.0)*t; |
50 |
tpmh[1] = (-6.0*t + 6.0)*t; |
51 |
tpmh[2] = (3.0*t - 4.0)*t + 1.0; |
52 |
tpmh[3] = (3.0*t - 2.0)*t; |
53 |
|
54 |
for (i = 0; i < 3; i++) |
55 |
ht[i] = p0[i]*tpmh[0] + p1[i]*tpmh[1] + |
56 |
r0[i]*tpmh[2] + r1[i]*tpmh[3]; |
57 |
} |