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root/radiance/ray/src/common/zeroes.c
Revision: 2.5
Committed: Thu Jul 17 09:21:29 2003 UTC (20 years, 8 months ago) by schorsch
Content type: text/plain
Branch: MAIN
CVS Tags: rad5R4, rad5R2, rad4R2P2, rad5R0, rad5R1, rad3R7P2, rad3R7P1, rad4R2, rad4R1, rad4R0, rad3R6, rad3R6P1, rad3R8, rad3R9, rad4R2P1, rad5R3, HEAD
Changes since 2.4: +2 -2 lines
Log Message:
Added prototypes and includes from patch by Randolph Fritz.
Added more required includes and reduced other compile warnings.

File Contents

# Content
1 #ifndef lint
2 static const char RCSid[] = "$Id: zeroes.c,v 2.4 2003/02/25 02:47:22 greg Exp $";
3 #endif
4 /*
5 * zeroes.c - compute roots for various equations.
6 *
7 * External symbols declared in standard.h
8 */
9
10 #include "copyright.h"
11
12
13 #include <math.h>
14
15 #include "fvect.h"
16 #include "rtmath.h"
17
18 int
19 quadratic(r, a, b, c) /* find real roots of quadratic equation */
20 double *r; /* roots in ascending order */
21 double a, b, c;
22 {
23 double disc;
24 int first;
25
26 if (a < -FTINY)
27 first = 1;
28 else if (a > FTINY)
29 first = 0;
30 else if (fabs(b) > FTINY) { /* solve linearly */
31 r[0] = -c/b;
32 return(1);
33 } else
34 return(0); /* equation is c == 0 ! */
35
36 b *= 0.5; /* simplifies formula */
37
38 disc = b*b - a*c; /* discriminant */
39
40 if (disc < -FTINY*FTINY) /* no real roots */
41 return(0);
42
43 if (disc <= FTINY*FTINY) { /* double root */
44 r[0] = -b/a;
45 return(1);
46 }
47
48 disc = sqrt(disc);
49
50 r[first] = (-b - disc)/a;
51 r[1-first] = (-b + disc)/a;
52
53 return(2);
54 }