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root/radiance/ray/src/ot/o_face.c
Revision: 2.3
Committed: Sun Jul 27 22:12:03 2003 UTC (21 years, 3 months ago) by schorsch
Content type: text/plain
Branch: MAIN
Changes since 2.2: +2 -2 lines
Log Message:
Added grouping parens to reduce ambiguity warnings.

File Contents

# Content
1 #ifndef lint
2 static const char RCSid[] = "$Id: o_face.c,v 2.2 2003/02/22 02:07:26 greg Exp $";
3 #endif
4 /*
5 * o_face.c - routines for creating octrees for polygonal faces.
6 *
7 * 8/27/85
8 */
9
10 #include "standard.h"
11
12 #include "octree.h"
13
14 #include "object.h"
15
16 #include "face.h"
17
18 #include "plocate.h"
19
20 /*
21 * The algorithm for determining a face's intersection
22 * with a cube is relatively straightforward:
23 *
24 * 1) Check to see if any vertices are inside the cube
25 * (intersection).
26 *
27 * 2) Check to see if all vertices are to one side of
28 * cube (no intersection).
29 *
30 * 3) Check to see if any portion of any edge is inside
31 * cube (intersection).
32 *
33 * 4) Check to see if the cube cuts the plane of the
34 * face and one of its edges passes through
35 * the face (intersection).
36 *
37 * 5) If test 4 fails, we have no intersection.
38 */
39
40
41 o_face(o, cu) /* determine if face intersects cube */
42 OBJREC *o;
43 CUBE *cu;
44 {
45 FVECT cumin, cumax;
46 FVECT v1, v2;
47 double d1, d2;
48 int vloc;
49 register FACE *f;
50 register int i, j;
51 /* get face arguments */
52 f = getface(o);
53 if (f->area == 0.0) /* empty face */
54 return(O_MISS);
55 /* compute cube boundaries */
56 for (j = 0; j < 3; j++)
57 cumax[j] = (cumin[j] = cu->cuorg[j]-FTINY)
58 + cu->cusize + 2.0*FTINY;
59
60 vloc = ABOVE | BELOW; /* check vertices */
61 for (i = 0; i < f->nv; i++)
62 if ( (j = plocate(VERTEX(f,i), cumin, cumax)) )
63 vloc &= j;
64 else
65 return(O_HIT); /* vertex inside */
66
67 if (vloc) /* all to one side */
68 return(O_MISS);
69
70 for (i = 0; i < f->nv; i++) { /* check edges */
71 if ((j = i + 1) >= f->nv)
72 j = 0; /* wrap around */
73 VCOPY(v1, VERTEX(f,i)); /* clip modifies */
74 VCOPY(v2, VERTEX(f,j)); /* the vertices! */
75 if (clip(v1, v2, cumin, cumax))
76 return(O_HIT); /* edge inside */
77 }
78 /* see if cube cuts plane */
79 for (j = 0; j < 3; j++)
80 if (f->norm[j] > 0.0) {
81 v1[j] = cumin[j];
82 v2[j] = cumax[j];
83 } else {
84 v1[j] = cumax[j];
85 v2[j] = cumin[j];
86 }
87 if ((d1 = DOT(v1, f->norm) - f->offset) > FTINY)
88 return(O_MISS);
89 if ((d2 = DOT(v2, f->norm) - f->offset) < -FTINY)
90 return(O_MISS);
91 /* intersect face */
92 for (j = 0; j < 3; j++)
93 v1[j] = (v1[j]*d2 - v2[j]*d1)/(d2 - d1);
94 if (inface(v1, f))
95 return(O_HIT);
96
97 return(O_MISS); /* no intersection */
98 }