| 1 |
#ifndef lint
|
| 2 |
static const char RCSid[] = "$Id$";
|
| 3 |
#endif
|
| 4 |
/*
|
| 5 |
* face.c - routines dealing with polygonal faces.
|
| 6 |
*/
|
| 7 |
|
| 8 |
#include "copyright.h"
|
| 9 |
|
| 10 |
#include "standard.h"
|
| 11 |
|
| 12 |
#include "object.h"
|
| 13 |
|
| 14 |
#include "face.h"
|
| 15 |
|
| 16 |
/*
|
| 17 |
* A face is given as a list of 3D vertices. The normal
|
| 18 |
* direction and therefore the surface orientation is determined
|
| 19 |
* by the ordering of the vertices. Looking in the direction opposite
|
| 20 |
* the normal (at the front of the face), the vertices will be
|
| 21 |
* listed in counter-clockwise order.
|
| 22 |
* There is no checking done to insure that the edges do not cross
|
| 23 |
* one another. This was considered too expensive and should be unnecessary.
|
| 24 |
* The last vertex is automatically connected to the first.
|
| 25 |
*/
|
| 26 |
|
| 27 |
#ifdef SMLFLT
|
| 28 |
#define VERTEPS 1e-3 /* allowed vertex error */
|
| 29 |
#else
|
| 30 |
#define VERTEPS 1e-5 /* allowed vertex error */
|
| 31 |
#endif
|
| 32 |
|
| 33 |
|
| 34 |
FACE *
|
| 35 |
getface(o) /* get arguments for a face */
|
| 36 |
OBJREC *o;
|
| 37 |
{
|
| 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 |
o->os = (char *)f; /* save face */
|
| 55 |
|
| 56 |
f->va = o->oargs.farg;
|
| 57 |
f->nv = o->oargs.nfargs / 3;
|
| 58 |
/* check for last==first */
|
| 59 |
if (dist2(VERTEX(f,0),VERTEX(f,f->nv-1)) <= FTINY*FTINY)
|
| 60 |
f->nv--;
|
| 61 |
/* compute area and normal */
|
| 62 |
f->norm[0] = f->norm[1] = f->norm[2] = 0.0;
|
| 63 |
v1[0] = VERTEX(f,1)[0] - VERTEX(f,0)[0];
|
| 64 |
v1[1] = VERTEX(f,1)[1] - VERTEX(f,0)[1];
|
| 65 |
v1[2] = VERTEX(f,1)[2] - VERTEX(f,0)[2];
|
| 66 |
for (i = 2; i < f->nv; i++) {
|
| 67 |
v2[0] = VERTEX(f,i)[0] - VERTEX(f,0)[0];
|
| 68 |
v2[1] = VERTEX(f,i)[1] - VERTEX(f,0)[1];
|
| 69 |
v2[2] = VERTEX(f,i)[2] - VERTEX(f,0)[2];
|
| 70 |
fcross(v3, v1, v2);
|
| 71 |
f->norm[0] += v3[0];
|
| 72 |
f->norm[1] += v3[1];
|
| 73 |
f->norm[2] += v3[2];
|
| 74 |
VCOPY(v1, v2);
|
| 75 |
}
|
| 76 |
f->area = normalize(f->norm);
|
| 77 |
if (f->area == 0.0) {
|
| 78 |
objerror(o, WARNING, "zero area"); /* used to be fatal */
|
| 79 |
f->offset = 0.0;
|
| 80 |
f->ax = 0;
|
| 81 |
return(f);
|
| 82 |
}
|
| 83 |
f->area *= 0.5;
|
| 84 |
/* compute offset */
|
| 85 |
badvert = 0;
|
| 86 |
f->offset = DOT(f->norm, VERTEX(f,0));
|
| 87 |
for (i = 1; i < f->nv; i++) {
|
| 88 |
d1 = DOT(f->norm, VERTEX(f,i));
|
| 89 |
badvert += fabs(1.0 - d1*i/f->offset) > VERTEPS;
|
| 90 |
f->offset += d1;
|
| 91 |
}
|
| 92 |
f->offset /= (double)f->nv;
|
| 93 |
if (f->nv > 3 && badvert)
|
| 94 |
objerror(o, WARNING, "non-planar vertex");
|
| 95 |
/* find axis */
|
| 96 |
f->ax = fabs(f->norm[0]) > fabs(f->norm[1]) ? 0 : 1;
|
| 97 |
if (fabs(f->norm[2]) > fabs(f->norm[f->ax]))
|
| 98 |
f->ax = 2;
|
| 99 |
|
| 100 |
return(f);
|
| 101 |
}
|
| 102 |
|
| 103 |
|
| 104 |
void
|
| 105 |
freeface(o) /* free memory associated with face */
|
| 106 |
OBJREC *o;
|
| 107 |
{
|
| 108 |
if (o->os == NULL)
|
| 109 |
return;
|
| 110 |
free(o->os);
|
| 111 |
o->os = NULL;
|
| 112 |
}
|
| 113 |
|
| 114 |
|
| 115 |
int
|
| 116 |
inface(p, f) /* determine if point is in face */
|
| 117 |
FVECT p;
|
| 118 |
FACE *f;
|
| 119 |
{
|
| 120 |
int ncross, n;
|
| 121 |
double x, y;
|
| 122 |
int tst;
|
| 123 |
register int xi, yi;
|
| 124 |
register FLOAT *p0, *p1;
|
| 125 |
|
| 126 |
xi = (f->ax+1)%3;
|
| 127 |
yi = (f->ax+2)%3;
|
| 128 |
x = p[xi];
|
| 129 |
y = p[yi];
|
| 130 |
n = f->nv;
|
| 131 |
p0 = f->va + 3*(n-1); /* connect last to first */
|
| 132 |
p1 = f->va;
|
| 133 |
ncross = 0;
|
| 134 |
/* positive x axis cross test */
|
| 135 |
while (n--) {
|
| 136 |
if ((p0[yi] > y) ^ (p1[yi] > y)) {
|
| 137 |
tst = (p0[xi] > x) + (p1[xi] > x);
|
| 138 |
if (tst == 2)
|
| 139 |
ncross++;
|
| 140 |
else if (tst)
|
| 141 |
ncross += (p1[yi] > p0[yi]) ^
|
| 142 |
((p0[yi]-y)*(p1[xi]-x) >
|
| 143 |
(p0[xi]-x)*(p1[yi]-y));
|
| 144 |
}
|
| 145 |
p0 = p1;
|
| 146 |
p1 += 3;
|
| 147 |
}
|
| 148 |
return(ncross & 01);
|
| 149 |
}
|
