src/common/face.c

/* Copyright (c) 1991 Regents of the University of California */

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

/*
 *  face.c - routines dealing with polygonal faces.
 *
 *     8/30/85
 */

#include  "standard.h"

#include  "object.h"

#include  "face.h"

/*
 *      A face is given as a list of 3D vertices.  The normal
 *  direction and therefore the surface orientation is determined
 *  by the ordering of the vertices.  Looking in the direction opposite
 *  the normal (at the front of the face), the vertices will be
 *  listed in counter-clockwise order.
 *      There is no checking done to insure that the edges do not cross
 *  one another.  This was considered too expensive and should be unnecessary.
 *  The last vertex is automatically connected to the first.
 */

#define  VERTEPS        1e-4            /* allowed vertex error */


FACE *
getface(o)                      /* get arguments for a face */
OBJREC  *o;
{
        double  fabs();
        double  d1;
        int  badvert;
        FVECT  v1, v2, v3;
        register FACE  *f;
        register int  i;

        if ((f = (FACE *)o->os) != NULL)
                return(f);                      /* already done */

        f = (FACE *)malloc(sizeof(FACE));
        if (f == NULL)
                error(SYSTEM, "out of memory in makeface");

        if (o->oargs.nfargs < 9 || o->oargs.nfargs % 3)
                objerror(o, USER, "bad # arguments");

        o->os = (char *)f;                      /* save face */

        f->va = o->oargs.farg;
        f->nv = o->oargs.nfargs / 3;
                                                /* compute area and normal */
        f->norm[0] = f->norm[1] = f->norm[2] = 0.0;
        v1[0] = v1[1] = v1[2] = 0.0;
        for (i = 1; i < f->nv; i++) {
                v2[0] = VERTEX(f,i)[0] - VERTEX(f,0)[0];
                v2[1] = VERTEX(f,i)[1] - VERTEX(f,0)[1];
                v2[2] = VERTEX(f,i)[2] - VERTEX(f,0)[2];
                fcross(v3, v1, v2);
                f->norm[0] += v3[0];
                f->norm[1] += v3[1];
                f->norm[2] += v3[2];
                VCOPY(v1, v2);
        }
        f->area = normalize(f->norm);
        if (f->area == 0.0) {
                objerror(o, WARNING, "zero area");      /* used to be fatal */
                f->offset = 0.0;
                f->ax = 0;
                return(f);
        }
        f->area *= 0.5;
                                                /* compute offset */
        badvert = 0;
        f->offset = DOT(f->norm, VERTEX(f,0));
        for (i = 1; i < f->nv; i++) {
                d1 = DOT(f->norm, VERTEX(f,i));
                badvert += fabs(d1 - f->offset/i) > VERTEPS;
                f->offset += d1;
        }
        f->offset /= (double)f->nv;
        if (badvert)
                objerror(o, WARNING, "non-planar vertex");
                                                /* find axis */
        f->ax = fabs(f->norm[0]) > fabs(f->norm[1]) ? 0 : 1;
        if (fabs(f->norm[2]) > fabs(f->norm[f->ax]))
                f->ax = 2;

        return(f);
}


freeface(o)                     /* free memory associated with face */
OBJREC  *o;
{
        if (o->os == NULL)
                return;
        free(o->os);
        o->os = NULL;
}


inface(p, f)                    /* determine if point is in face */
FVECT  p;
FACE  *f;
{
        int  ncross, n;
        double  x, y;
        register int  xi, yi;
        register FLOAT  *p0, *p1;

        xi = (f->ax+1)%3;
        yi = (f->ax+2)%3;
        x = p[xi];
        y = p[yi];
        n = f->nv;
        p0 = f->va + 3*(n-1);           /* connect last to first */
        p1 = f->va;
        ncross = 0;
                                        /* positive x axis cross test */
        while (n--) {
                if ((p0[yi] > y) ^ (p1[yi] > y))
                        if (p0[xi] > x && p1[xi] > x)
                                ncross++;
                        else if (p0[xi] > x || p1[xi] > x)
                                ncross += (p1[yi] > p0[yi]) ^
                                                ((p0[yi]-y)*(p1[xi]-x) >
                                                (p0[xi]-x)*(p1[yi]-y));
                p0 = p1;
                p1 += 3;
        }
        return(ncross & 01);
}
Revision:	1.6
Committed:	Wed Oct 23 13:43:14 1991 UTC (32 years, 6 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.5:	+1 -1 lines
Log Message:	added FLOAT definition to better control size of structures
#	User	Rev	Content
1	greg	1.5	/* Copyright (c) 1991 Regents of the University of California */
2	greg	1.1
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* face.c - routines dealing with polygonal faces.
9			*
10			* 8/30/85
11			*/
12
13			#include "standard.h"
14
15			#include "object.h"
16
17			#include "face.h"
18
19			/*
20			* A face is given as a list of 3D vertices. The normal
21			* direction and therefore the surface orientation is determined
22			* by the ordering of the vertices. Looking in the direction opposite
23			* the normal (at the front of the face), the vertices will be
24			* listed in counter-clockwise order.
25			* There is no checking done to insure that the edges do not cross
26			* one another. This was considered too expensive and should be unnecessary.
27			* The last vertex is automatically connected to the first.
28			*/
29
30			#define VERTEPS 1e-4 /* allowed vertex error */
31
32
33			FACE *
34			getface(o) /* get arguments for a face */
35			OBJREC *o;
36			{
37			double fabs();
38			double d1;
39			int badvert;
40			FVECT v1, v2, v3;
41			register FACE *f;
42			register int i;
43
44			if ((f = (FACE *)o->os) != NULL)
45			return(f); /* already done */
46
47			f = (FACE *)malloc(sizeof(FACE));
48			if (f == NULL)
49			error(SYSTEM, "out of memory in makeface");
50
51			if (o->oargs.nfargs < 9 \|\| o->oargs.nfargs % 3)
52			objerror(o, USER, "bad # arguments");
53
54	greg	1.3	o->os = (char )f; / save face */
55
56	greg	1.1	f->va = o->oargs.farg;
57			f->nv = o->oargs.nfargs / 3;
58			/* compute area and normal */
59			f->norm[0] = f->norm[1] = f->norm[2] = 0.0;
60			v1[0] = v1[1] = v1[2] = 0.0;
61			for (i = 1; i < f->nv; i++) {
62			v2[0] = VERTEX(f,i)[0] - VERTEX(f,0)[0];
63			v2[1] = VERTEX(f,i)[1] - VERTEX(f,0)[1];
64			v2[2] = VERTEX(f,i)[2] - VERTEX(f,0)[2];
65			fcross(v3, v1, v2);
66			f->norm[0] += v3[0];
67			f->norm[1] += v3[1];
68			f->norm[2] += v3[2];
69			VCOPY(v1, v2);
70			}
71			f->area = normalize(f->norm);
72			if (f->area == 0.0) {
73			objerror(o, WARNING, "zero area"); /* used to be fatal */
74	greg	1.2	f->offset = 0.0;
75	greg	1.1	f->ax = 0;
76			return(f);
77			}
78			f->area *= 0.5;
79	greg	1.2	/* compute offset */
80	greg	1.1	badvert = 0;
81	greg	1.2	f->offset = DOT(f->norm, VERTEX(f,0));
82	greg	1.1	for (i = 1; i < f->nv; i++) {
83			d1 = DOT(f->norm, VERTEX(f,i));
84	greg	1.2	badvert += fabs(d1 - f->offset/i) > VERTEPS;
85			f->offset += d1;
86	greg	1.1	}
87	greg	1.5	f->offset /= (double)f->nv;
88	greg	1.1	if (badvert)
89			objerror(o, WARNING, "non-planar vertex");
90			/* find axis */
91			f->ax = fabs(f->norm[0]) > fabs(f->norm[1]) ? 0 : 1;
92			if (fabs(f->norm[2]) > fabs(f->norm[f->ax]))
93			f->ax = 2;
94
95			return(f);
96			}
97
98
99			freeface(o) /* free memory associated with face */
100			OBJREC *o;
101			{
102	greg	1.4	if (o->os == NULL)
103			return;
104	greg	1.1	free(o->os);
105			o->os = NULL;
106			}
107
108
109			inface(p, f) /* determine if point is in face */
110			FVECT p;
111			FACE *f;
112			{
113			int ncross, n;
114			double x, y;
115			register int xi, yi;
116	greg	1.6	register FLOAT p0, p1;
117	greg	1.1
118			xi = (f->ax+1)%3;
119			yi = (f->ax+2)%3;
120			x = p[xi];
121			y = p[yi];
122			n = f->nv;
123			p0 = f->va + 3(n-1); / connect last to first */
124			p1 = f->va;
125			ncross = 0;
126			/* positive x axis cross test */
127			while (n--) {
128			if ((p0[yi] > y) ^ (p1[yi] > y))
129			if (p0[xi] > x && p1[xi] > x)
130			ncross++;
131			else if (p0[xi] > x \|\| p1[xi] > x)
132			ncross += (p1[yi] > p0[yi]) ^
133			((p0[yi]-y)*(p1[xi]-x) >
134			(p0[xi]-x)*(p1[yi]-y));
135			p0 = p1;
136			p1 += 3;
137			}
138			return(ncross & 01);
139			}