src/rt/sphere.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 *  sphere.c - compute ray intersection with spheres.
 */

/* ====================================================================
 * The Radiance Software License, Version 1.0
 *
 * Copyright (c) 1990 - 2002 The Regents of the University of California,
 * through Lawrence Berkeley National Laboratory.   All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *         notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in
 *       the documentation and/or other materials provided with the
 *       distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *           if any, must include the following acknowledgment:
 *             "This product includes Radiance software
 *                 (http://radsite.lbl.gov/)
 *                 developed by the Lawrence Berkeley National Laboratory
 *               (http://www.lbl.gov/)."
 *       Alternately, this acknowledgment may appear in the software itself,
 *       if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
 *       and "The Regents of the University of California" must
 *       not be used to endorse or promote products derived from this
 *       software without prior written permission. For written
 *       permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Radiance",
 *       nor may "Radiance" appear in their name, without prior written
 *       permission of Lawrence Berkeley National Laboratory.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.   IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Lawrence Berkeley National Laboratory.   For more
 * information on Lawrence Berkeley National Laboratory, please see
 * <http://www.lbl.gov/>.
 */

#include  "ray.h"

#include  "otypes.h"


o_sphere(so, r)                 /* compute intersection with sphere */
OBJREC  *so;
register RAY  *r;
{
        double  a, b, c;        /* coefficients for quadratic equation */
        double  root[2];        /* quadratic roots */
        int  nroots;
        double  t;
        register FLOAT  *ap;
        register int  i;

        if (so->oargs.nfargs != 4)
                objerror(so, USER, "bad # arguments");
        ap = so->oargs.farg;
        if (ap[3] < -FTINY) {
                objerror(so, WARNING, "negative radius");
                so->otype = so->otype == OBJ_SPHERE ?
                                OBJ_BUBBLE : OBJ_SPHERE;
                ap[3] = -ap[3];
        } else if (ap[3] <= FTINY)
                objerror(so, USER, "zero radius");

        /*
         *      We compute the intersection by substituting into
         *  the surface equation for the sphere.  The resulting
         *  quadratic equation in t is then solved for the
         *  smallest positive root, which is our point of
         *  intersection.
         *      Since the ray is normalized, a should always be
         *  one.  We compute it here to prevent instability in the
         *  intersection calculation.
         */
                                /* compute quadratic coefficients */
        a = b = c = 0.0;
        for (i = 0; i < 3; i++) {
                a += r->rdir[i]*r->rdir[i];
                t = r->rorg[i] - ap[i];
                b += 2.0*r->rdir[i]*t;
                c += t*t;
        }
        c -= ap[3] * ap[3];

        nroots = quadratic(root, a, b, c);      /* solve quadratic */
        
        for (i = 0; i < nroots; i++)            /* get smallest positive */
                if ((t = root[i]) > FTINY)
                        break;
        if (i >= nroots)
                return(0);                      /* no positive root */

        if (t >= r->rot)
                return(0);                      /* other is closer */

        r->ro = so;
        r->rot = t;
                                        /* compute normal */
        a = ap[3];
        if (so->otype == OBJ_BUBBLE)
                a = -a;                 /* reverse */
        for (i = 0; i < 3; i++) {
                r->rop[i] = r->rorg[i] + r->rdir[i]*t;
                r->ron[i] = (r->rop[i] - ap[i]) / a;
        }
        r->rod = -DOT(r->rdir, r->ron);
        r->rox = NULL;

        return(1);                      /* hit */
}
Revision:	2.3
Committed:	Sat Feb 22 02:07:29 2003 UTC (22 years, 10 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.2:	+57 -5 lines
Log Message:	Changes and check-in for 3.5 release Includes new source files and modifications not recorded for many years See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release
#	Content
1	#ifndef lint
2	static const char RCSid[] = "$Id$";
3	#endif
4	/*
5	* sphere.c - compute ray intersection with spheres.
6	*/
7
8	/* ====================================================================
9	* The Radiance Software License, Version 1.0
10	*
11	* Copyright (c) 1990 - 2002 The Regents of the University of California,
12	* through Lawrence Berkeley National Laboratory. All rights reserved.
13	*
14	* Redistribution and use in source and binary forms, with or without
15	* modification, are permitted provided that the following conditions
16	* are met:
17	*
18	* 1. Redistributions of source code must retain the above copyright
19	* notice, this list of conditions and the following disclaimer.
20	*
21	* 2. Redistributions in binary form must reproduce the above copyright
22	* notice, this list of conditions and the following disclaimer in
23	* the documentation and/or other materials provided with the
24	* distribution.
25	*
26	* 3. The end-user documentation included with the redistribution,
27	* if any, must include the following acknowledgment:
28	* "This product includes Radiance software
29	* (http://radsite.lbl.gov/)
30	* developed by the Lawrence Berkeley National Laboratory
31	* (http://www.lbl.gov/)."
32	* Alternately, this acknowledgment may appear in the software itself,
33	* if and wherever such third-party acknowledgments normally appear.
34	*
35	* 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
36	* and "The Regents of the University of California" must
37	* not be used to endorse or promote products derived from this
38	* software without prior written permission. For written
39	* permission, please contact [email protected].
40	*
41	* 5. Products derived from this software may not be called "Radiance",
42	* nor may "Radiance" appear in their name, without prior written
43	* permission of Lawrence Berkeley National Laboratory.
44	*
45	* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
46	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
47	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
48	* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
49	* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
50	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
51	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
52	* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
53	* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
54	* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
55	* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
56	* SUCH DAMAGE.
57	* ====================================================================
58	*
59	* This software consists of voluntary contributions made by many
60	* individuals on behalf of Lawrence Berkeley National Laboratory. For more
61	* information on Lawrence Berkeley National Laboratory, please see
62	* <http://www.lbl.gov/>.
63	*/
64
65	#include "ray.h"
66
67	#include "otypes.h"
68
69
70	o_sphere(so, r) /* compute intersection with sphere */
71	OBJREC *so;
72	register RAY *r;
73	{
74	double a, b, c; /* coefficients for quadratic equation */
75	double root[2]; /* quadratic roots */
76	int nroots;
77	double t;
78	register FLOAT *ap;
79	register int i;
80
81	if (so->oargs.nfargs != 4)
82	objerror(so, USER, "bad # arguments");
83	ap = so->oargs.farg;
84	if (ap[3] < -FTINY) {
85	objerror(so, WARNING, "negative radius");
86	so->otype = so->otype == OBJ_SPHERE ?
87	OBJ_BUBBLE : OBJ_SPHERE;
88	ap[3] = -ap[3];
89	} else if (ap[3] <= FTINY)
90	objerror(so, USER, "zero radius");
91
92	/*
93	* We compute the intersection by substituting into
94	* the surface equation for the sphere. The resulting
95	* quadratic equation in t is then solved for the
96	* smallest positive root, which is our point of
97	* intersection.
98	* Since the ray is normalized, a should always be
99	* one. We compute it here to prevent instability in the
100	* intersection calculation.
101	*/
102	/* compute quadratic coefficients */
103	a = b = c = 0.0;
104	for (i = 0; i < 3; i++) {
105	a += r->rdir[i]*r->rdir[i];
106	t = r->rorg[i] - ap[i];
107	b += 2.0r->rdir[i]t;
108	c += t*t;
109	}
110	c -= ap[3] * ap[3];
111
112	nroots = quadratic(root, a, b, c); /* solve quadratic */
113
114	for (i = 0; i < nroots; i++) /* get smallest positive */
115	if ((t = root[i]) > FTINY)
116	break;
117	if (i >= nroots)
118	return(0); /* no positive root */
119
120	if (t >= r->rot)
121	return(0); /* other is closer */
122
123	r->ro = so;
124	r->rot = t;
125	/* compute normal */
126	a = ap[3];
127	if (so->otype == OBJ_BUBBLE)
128	a = -a; /* reverse */
129	for (i = 0; i < 3; i++) {
130	r->rop[i] = r->rorg[i] + r->rdir[i]*t;
131	r->ron[i] = (r->rop[i] - ap[i]) / a;
132	}
133	r->rod = -DOT(r->rdir, r->ron);
134	r->rox = NULL;
135
136	return(1); /* hit */
137	}