| 1 |
greg |
1.1 |
/* Copyright (c) 1986 Regents of the University of California */ |
| 2 |
|
|
|
| 3 |
|
|
#ifndef lint |
| 4 |
|
|
static char SCCSid[] = "$SunId$ LBL"; |
| 5 |
|
|
#endif |
| 6 |
|
|
|
| 7 |
|
|
/* |
| 8 |
|
|
* sphere.c - compute ray intersection with spheres. |
| 9 |
|
|
* |
| 10 |
|
|
* 8/19/85 |
| 11 |
|
|
*/ |
| 12 |
|
|
|
| 13 |
|
|
#include "ray.h" |
| 14 |
|
|
|
| 15 |
|
|
#include "otypes.h" |
| 16 |
|
|
|
| 17 |
|
|
|
| 18 |
|
|
o_sphere(so, r) /* compute intersection with sphere */ |
| 19 |
|
|
OBJREC *so; |
| 20 |
|
|
register RAY *r; |
| 21 |
|
|
{ |
| 22 |
|
|
double a, b, c; /* coefficients for quadratic equation */ |
| 23 |
|
|
double root[2]; /* quadratic roots */ |
| 24 |
|
|
int nroots; |
| 25 |
|
|
double t; |
| 26 |
|
|
register double *ap; |
| 27 |
|
|
register int i; |
| 28 |
|
|
|
| 29 |
|
|
if (so->oargs.nfargs != 4 || so->oargs.farg[3] <= FTINY) |
| 30 |
|
|
objerror(so, USER, "bad arguments"); |
| 31 |
|
|
|
| 32 |
|
|
ap = so->oargs.farg; |
| 33 |
|
|
|
| 34 |
|
|
/* |
| 35 |
|
|
* We compute the intersection by substituting into |
| 36 |
|
|
* the surface equation for the sphere. The resulting |
| 37 |
|
|
* quadratic equation in t is then solved for the |
| 38 |
|
|
* smallest positive root, which is our point of |
| 39 |
|
|
* intersection. |
| 40 |
|
|
* Because the ray direction is normalized, a is always 1. |
| 41 |
|
|
*/ |
| 42 |
|
|
|
| 43 |
|
|
a = 1.0; /* compute quadratic coefficients */ |
| 44 |
|
|
b = c = 0.0; |
| 45 |
|
|
for (i = 0; i < 3; i++) { |
| 46 |
|
|
t = r->rorg[i] - ap[i]; |
| 47 |
|
|
b += 2.0*r->rdir[i]*t; |
| 48 |
|
|
c += t*t; |
| 49 |
|
|
} |
| 50 |
|
|
c -= ap[3] * ap[3]; |
| 51 |
|
|
|
| 52 |
|
|
nroots = quadratic(root, a, b, c); /* solve quadratic */ |
| 53 |
|
|
|
| 54 |
|
|
for (i = 0; i < nroots; i++) /* get smallest positive */ |
| 55 |
|
|
if ((t = root[i]) > FTINY) |
| 56 |
|
|
break; |
| 57 |
|
|
if (i >= nroots) |
| 58 |
|
|
return(0); /* no positive root */ |
| 59 |
|
|
|
| 60 |
|
|
if (t < r->rot) { /* found closer intersection */ |
| 61 |
|
|
r->ro = so; |
| 62 |
|
|
r->rot = t; |
| 63 |
|
|
/* compute normal */ |
| 64 |
|
|
a = ap[3]; |
| 65 |
|
|
if (so->otype == OBJ_BUBBLE) |
| 66 |
|
|
a = -a; /* reverse */ |
| 67 |
|
|
for (i = 0; i < 3; i++) { |
| 68 |
|
|
r->rop[i] = r->rorg[i] + r->rdir[i]*t; |
| 69 |
|
|
r->ron[i] = (r->rop[i] - ap[i]) / a; |
| 70 |
|
|
} |
| 71 |
|
|
r->rod = -DOT(r->rdir, r->ron); |
| 72 |
|
|
} |
| 73 |
|
|
return(1); |
| 74 |
|
|
} |
