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root/radiance/ray/src/ot/o_face.c
Revision: 2.5
Committed: Tue Mar 30 16:13:00 2004 UTC (20 years 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 -3 lines
Log Message:
Continued ANSIfication. There are only bits and pieces left now.

File Contents

# User Rev Content
1 greg 1.1 #ifndef lint
2 schorsch 2.5 static const char RCSid[] = "$Id: o_face.c,v 2.4 2004/03/27 12:41:45 schorsch Exp $";
3 greg 1.1 #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 schorsch 2.4 int
41 schorsch 2.5 o_face( /* determine if face intersects cube */
42 schorsch 2.4 OBJREC *o,
43     CUBE *cu
44     )
45 greg 1.1 {
46     FVECT cumin, cumax;
47     FVECT v1, v2;
48     double d1, d2;
49     int vloc;
50     register FACE *f;
51     register int i, j;
52     /* get face arguments */
53     f = getface(o);
54     if (f->area == 0.0) /* empty face */
55 greg 1.3 return(O_MISS);
56 greg 1.1 /* compute cube boundaries */
57     for (j = 0; j < 3; j++)
58 greg 1.4 cumax[j] = (cumin[j] = cu->cuorg[j]-FTINY)
59     + cu->cusize + 2.0*FTINY;
60 greg 1.1
61     vloc = ABOVE | BELOW; /* check vertices */
62     for (i = 0; i < f->nv; i++)
63 schorsch 2.3 if ( (j = plocate(VERTEX(f,i), cumin, cumax)) )
64 greg 1.1 vloc &= j;
65     else
66 greg 1.3 return(O_HIT); /* vertex inside */
67 greg 1.1
68     if (vloc) /* all to one side */
69 greg 1.3 return(O_MISS);
70 greg 1.1
71     for (i = 0; i < f->nv; i++) { /* check edges */
72     if ((j = i + 1) >= f->nv)
73     j = 0; /* wrap around */
74     VCOPY(v1, VERTEX(f,i)); /* clip modifies */
75     VCOPY(v2, VERTEX(f,j)); /* the vertices! */
76     if (clip(v1, v2, cumin, cumax))
77 greg 1.3 return(O_HIT); /* edge inside */
78 greg 1.1 }
79     /* see if cube cuts plane */
80     for (j = 0; j < 3; j++)
81     if (f->norm[j] > 0.0) {
82     v1[j] = cumin[j];
83     v2[j] = cumax[j];
84     } else {
85     v1[j] = cumax[j];
86     v2[j] = cumin[j];
87     }
88 greg 1.2 if ((d1 = DOT(v1, f->norm) - f->offset) > FTINY)
89 greg 1.3 return(O_MISS);
90 greg 1.2 if ((d2 = DOT(v2, f->norm) - f->offset) < -FTINY)
91 greg 1.3 return(O_MISS);
92 greg 1.1 /* intersect face */
93     for (j = 0; j < 3; j++)
94     v1[j] = (v1[j]*d2 - v2[j]*d1)/(d2 - d1);
95     if (inface(v1, f))
96 greg 1.3 return(O_HIT);
97 greg 1.1
98 greg 1.3 return(O_MISS); /* no intersection */
99 greg 1.1 }