src/rt/o_cone.c

/* Copyright (c) 1990 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 *  o_cone.c - routine to determine ray intersection with cones.
 *
 *     2/13/86
 */

#include  "ray.h"

#include  "otypes.h"

#include  "cone.h"


o_cone(o, r)                    /* intersect ray with cone */
OBJREC  *o;
register RAY  *r;
{
        FVECT  rox, rdx;
        double  a, b, c;
        double  root[2];
        int  nroots, rn;
        register CONE  *co;
        register int  i;

                                                /* get cone structure */
        co = getcone(o, 1);

        /*
         *     To intersect a ray with a cone, we transform the
         *  ray into the cone's normalized space.  This greatly
         *  simplifies the computation.
         *     For a cone or cup, normalization results in the
         *  equation:
         *
         *              x*x + y*y - z*z == 0
         *
         *     For a cylinder or tube, the normalized equation is:
         *
         *              x*x + y*y - r*r == 0
         *
         *     A normalized ring obeys the following set of equations:
         *
         *              z == 0                  &&
         *              x*x + y*y >= r0*r0      &&
         *              x*x + y*y <= r1*r1
         */

                                        /* transform ray */
        multp3(rox, r->rorg, co->tm);
        multv3(rdx, r->rdir, co->tm);
                                        /* compute intersection */

        if (o->otype == OBJ_CONE || o->otype == OBJ_CUP) {

                a = rdx[0]*rdx[0] + rdx[1]*rdx[1] - rdx[2]*rdx[2];
                b = 2.0*(rdx[0]*rox[0] + rdx[1]*rox[1] - rdx[2]*rox[2]);
                c = rox[0]*rox[0] + rox[1]*rox[1] - rox[2]*rox[2];

        } else if (o->otype == OBJ_CYLINDER || o->otype == OBJ_TUBE) {

                a = rdx[0]*rdx[0] + rdx[1]*rdx[1];
                b = 2.0*(rdx[0]*rox[0] + rdx[1]*rox[1]);
                c = rox[0]*rox[0] + rox[1]*rox[1] - CO_R0(co)*CO_R0(co);

        } else { /* OBJ_RING */

                if (rdx[2] <= FTINY && rdx[2] >= -FTINY)
                        return(0);                      /* parallel */
                root[0] = -rox[2]/rdx[2];
                if (root[0] <= FTINY || root[0] >= r->rot)
                        return(0);                      /* distance check */
                b = root[0]*rdx[0] + rox[0];
                c = root[0]*rdx[1] + rox[1];
                a = b*b + c*c;
                if (a < CO_R0(co)*CO_R0(co) || a > CO_R1(co)*CO_R1(co))
                        return(0);                      /* outside radii */
                r->ro = o;
                r->rot = root[0];
                for (i = 0; i < 3; i++)
                        r->rop[i] = r->rorg[i] + r->rdir[i]*r->rot;
                VCOPY(r->ron, co->ad);
                r->rod = -rdx[2];
                r->rox = NULL;
                return(1);                              /* good */
        }
                                        /* roots for cone, cup, cyl., tube */
        nroots = quadratic(root, a, b, c);

        for (rn = 0; rn < nroots; rn++) {       /* check real roots */
                if (root[rn] <= FTINY)
                        continue;               /* too small */
                if (root[rn] >= r->rot)
                        break;                  /* too big */
                                                /* check endpoints */
                for (i = 0; i < 3; i++) {
                        rox[i] = r->rorg[i] + root[rn]*r->rdir[i];
                        rdx[i] = rox[i] - CO_P0(co)[i];
                }
                b = DOT(rdx, co->ad); 
                if (b < 0.0)
                        continue;               /* before p0 */
                if (b > co->al)
                        continue;               /* after p1 */
                r->ro = o;
                r->rot = root[rn];
                VCOPY(r->rop, rox);
                                                /* get normal */
                if (o->otype == OBJ_CYLINDER)
                        a = CO_R0(co);
                else if (o->otype == OBJ_TUBE)
                        a = -CO_R0(co);
                else { /* OBJ_CONE || OBJ_CUP */
                        c = CO_R1(co) - CO_R0(co);
                        a = CO_R0(co) + b*c/co->al;
                        if (o->otype == OBJ_CUP) {
                                c = -c;
                                a = -a;
                        }
                }
                for (i = 0; i < 3; i++)
                        r->ron[i] = (rdx[i] - b*co->ad[i])/a;
                if (o->otype == OBJ_CONE || o->otype == OBJ_CUP)
                        for (i = 0; i < 3; i++)
                                r->ron[i] = (co->al*r->ron[i] - c*co->ad[i])
                                                /co->sl;
                r->rod = -DOT(r->rdir, r->ron);
                r->rox = NULL;
                return(1);                      /* good */
        }
        return(0);
}
Revision:	1.3
Committed:	Sat Dec 15 15:03:28 1990 UTC (33 years, 4 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.2:	+3 -5 lines
Log Message:	changed handling of matrix transformations with new MAT4 & XF types dynamic allocation of ray transformations with newrayxf() added missing light source vector transformation to m_brdf.c
#	User	Rev	Content
1	greg	1.3	/* Copyright (c) 1990 Regents of the University of California */
2	greg	1.1
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* o_cone.c - routine to determine ray intersection with cones.
9			*
10			* 2/13/86
11			*/
12
13			#include "ray.h"
14
15			#include "otypes.h"
16
17			#include "cone.h"
18
19
20			o_cone(o, r) /* intersect ray with cone */
21			OBJREC *o;
22			register RAY *r;
23			{
24			FVECT rox, rdx;
25			double a, b, c;
26			double root[2];
27			int nroots, rn;
28			register CONE *co;
29			register int i;
30
31			/* get cone structure */
32			co = getcone(o, 1);
33
34			/*
35			* To intersect a ray with a cone, we transform the
36			* ray into the cone's normalized space. This greatly
37			* simplifies the computation.
38			* For a cone or cup, normalization results in the
39			* equation:
40			*
41			* xx + yy - z*z == 0
42			*
43			* For a cylinder or tube, the normalized equation is:
44			*
45			* xx + yy - r*r == 0
46			*
47			* A normalized ring obeys the following set of equations:
48			*
49			* z == 0 &&
50			* xx + yy >= r0*r0 &&
51			* xx + yy <= r1*r1
52			*/
53
54			/* transform ray */
55			multp3(rox, r->rorg, co->tm);
56			multv3(rdx, r->rdir, co->tm);
57			/* compute intersection */
58
59			if (o->otype == OBJ_CONE \|\| o->otype == OBJ_CUP) {
60
61			a = rdx[0]rdx[0] + rdx[1]rdx[1] - rdx[2]*rdx[2];
62			b = 2.0(rdx[0]rox[0] + rdx[1]rox[1] - rdx[2]rox[2]);
63			c = rox[0]rox[0] + rox[1]rox[1] - rox[2]*rox[2];
64
65			} else if (o->otype == OBJ_CYLINDER \|\| o->otype == OBJ_TUBE) {
66
67			a = rdx[0]rdx[0] + rdx[1]rdx[1];
68			b = 2.0(rdx[0]rox[0] + rdx[1]*rox[1]);
69			c = rox[0]rox[0] + rox[1]rox[1] - CO_R0(co)*CO_R0(co);
70
71			} else { /* OBJ_RING */
72
73			if (rdx[2] <= FTINY && rdx[2] >= -FTINY)
74			return(0); /* parallel */
75			root[0] = -rox[2]/rdx[2];
76			if (root[0] <= FTINY \|\| root[0] >= r->rot)
77			return(0); /* distance check */
78			b = root[0]*rdx[0] + rox[0];
79			c = root[0]*rdx[1] + rox[1];
80			a = bb + cc;
81			if (a < CO_R0(co)CO_R0(co) \|\| a > CO_R1(co)CO_R1(co))
82			return(0); /* outside radii */
83			r->ro = o;
84			r->rot = root[0];
85			for (i = 0; i < 3; i++)
86			r->rop[i] = r->rorg[i] + r->rdir[i]*r->rot;
87			VCOPY(r->ron, co->ad);
88			r->rod = -rdx[2];
89	greg	1.3	r->rox = NULL;
90	greg	1.1	return(1); /* good */
91			}
92			/* roots for cone, cup, cyl., tube */
93			nroots = quadratic(root, a, b, c);
94
95			for (rn = 0; rn < nroots; rn++) { /* check real roots */
96			if (root[rn] <= FTINY)
97			continue; /* too small */
98			if (root[rn] >= r->rot)
99			break; /* too big */
100			/* check endpoints */
101			for (i = 0; i < 3; i++) {
102			rox[i] = r->rorg[i] + root[rn]*r->rdir[i];
103			rdx[i] = rox[i] - CO_P0(co)[i];
104			}
105			b = DOT(rdx, co->ad);
106			if (b < 0.0)
107			continue; /* before p0 */
108			if (b > co->al)
109			continue; /* after p1 */
110			r->ro = o;
111			r->rot = root[rn];
112			VCOPY(r->rop, rox);
113			/* get normal */
114			if (o->otype == OBJ_CYLINDER)
115			a = CO_R0(co);
116			else if (o->otype == OBJ_TUBE)
117			a = -CO_R0(co);
118			else { /* OBJ_CONE \|\| OBJ_CUP */
119			c = CO_R1(co) - CO_R0(co);
120			a = CO_R0(co) + b*c/co->al;
121			if (o->otype == OBJ_CUP) {
122			c = -c;
123			a = -a;
124			}
125			}
126			for (i = 0; i < 3; i++)
127			r->ron[i] = (rdx[i] - b*co->ad[i])/a;
128			if (o->otype == OBJ_CONE \|\| o->otype == OBJ_CUP)
129			for (i = 0; i < 3; i++)
130			r->ron[i] = (co->alr->ron[i] - cco->ad[i])
131			/co->sl;
132			r->rod = -DOT(r->rdir, r->ron);
133	greg	1.3	r->rox = NULL;
134	greg	1.1	return(1); /* good */
135			}
136			return(0);
137			}