| 1 |
/* Copyright (c) 1995 Regents of the University of California */ |
| 2 |
|
| 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 |
#ifdef SMLFLT |
| 31 |
#define VERTEPS 1e-2 /* allowed vertex error */ |
| 32 |
#else |
| 33 |
#define VERTEPS 1e-4 /* allowed vertex error */ |
| 34 |
#endif |
| 35 |
|
| 36 |
|
| 37 |
FACE * |
| 38 |
getface(o) /* get arguments for a face */ |
| 39 |
OBJREC *o; |
| 40 |
{ |
| 41 |
double d1; |
| 42 |
int badvert; |
| 43 |
FVECT v1, v2, v3; |
| 44 |
register FACE *f; |
| 45 |
register int i; |
| 46 |
|
| 47 |
if ((f = (FACE *)o->os) != NULL) |
| 48 |
return(f); /* already done */ |
| 49 |
|
| 50 |
f = (FACE *)malloc(sizeof(FACE)); |
| 51 |
if (f == NULL) |
| 52 |
error(SYSTEM, "out of memory in makeface"); |
| 53 |
|
| 54 |
if (o->oargs.nfargs < 9 || o->oargs.nfargs % 3) |
| 55 |
objerror(o, USER, "bad # arguments"); |
| 56 |
|
| 57 |
o->os = (char *)f; /* save face */ |
| 58 |
|
| 59 |
f->va = o->oargs.farg; |
| 60 |
f->nv = o->oargs.nfargs / 3; |
| 61 |
/* check for last==first */ |
| 62 |
if (dist2(VERTEX(f,0),VERTEX(f,f->nv-1)) <= FTINY*FTINY) |
| 63 |
f->nv--; |
| 64 |
/* compute area and normal */ |
| 65 |
f->norm[0] = f->norm[1] = f->norm[2] = 0.0; |
| 66 |
v1[0] = VERTEX(f,1)[0] - VERTEX(f,0)[0]; |
| 67 |
v1[1] = VERTEX(f,1)[1] - VERTEX(f,0)[1]; |
| 68 |
v1[2] = VERTEX(f,1)[2] - VERTEX(f,0)[2]; |
| 69 |
for (i = 2; i < f->nv; i++) { |
| 70 |
v2[0] = VERTEX(f,i)[0] - VERTEX(f,0)[0]; |
| 71 |
v2[1] = VERTEX(f,i)[1] - VERTEX(f,0)[1]; |
| 72 |
v2[2] = VERTEX(f,i)[2] - VERTEX(f,0)[2]; |
| 73 |
fcross(v3, v1, v2); |
| 74 |
f->norm[0] += v3[0]; |
| 75 |
f->norm[1] += v3[1]; |
| 76 |
f->norm[2] += v3[2]; |
| 77 |
VCOPY(v1, v2); |
| 78 |
} |
| 79 |
f->area = normalize(f->norm); |
| 80 |
if (f->area == 0.0) { |
| 81 |
objerror(o, WARNING, "zero area"); /* used to be fatal */ |
| 82 |
f->offset = 0.0; |
| 83 |
f->ax = 0; |
| 84 |
return(f); |
| 85 |
} |
| 86 |
f->area *= 0.5; |
| 87 |
/* compute offset */ |
| 88 |
badvert = 0; |
| 89 |
f->offset = DOT(f->norm, VERTEX(f,0)); |
| 90 |
for (i = 1; i < f->nv; i++) { |
| 91 |
d1 = DOT(f->norm, VERTEX(f,i)); |
| 92 |
badvert += fabs(d1 - f->offset/i) > VERTEPS; |
| 93 |
f->offset += d1; |
| 94 |
} |
| 95 |
f->offset /= (double)f->nv; |
| 96 |
if (badvert) |
| 97 |
objerror(o, WARNING, "non-planar vertex"); |
| 98 |
/* find axis */ |
| 99 |
f->ax = fabs(f->norm[0]) > fabs(f->norm[1]) ? 0 : 1; |
| 100 |
if (fabs(f->norm[2]) > fabs(f->norm[f->ax])) |
| 101 |
f->ax = 2; |
| 102 |
|
| 103 |
return(f); |
| 104 |
} |
| 105 |
|
| 106 |
|
| 107 |
freeface(o) /* free memory associated with face */ |
| 108 |
OBJREC *o; |
| 109 |
{ |
| 110 |
if (o->os == NULL) |
| 111 |
return; |
| 112 |
free(o->os); |
| 113 |
o->os = NULL; |
| 114 |
} |
| 115 |
|
| 116 |
|
| 117 |
inface(p, f) /* determine if point is in face */ |
| 118 |
FVECT p; |
| 119 |
FACE *f; |
| 120 |
{ |
| 121 |
int ncross, n; |
| 122 |
double x, y; |
| 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 |
if (p0[xi] > x && p1[xi] > x) |
| 138 |
ncross++; |
| 139 |
else if (p0[xi] > x || p1[xi] > x) |
| 140 |
ncross += (p1[yi] > p0[yi]) ^ |
| 141 |
((p0[yi]-y)*(p1[xi]-x) > |
| 142 |
(p0[xi]-x)*(p1[yi]-y)); |
| 143 |
p0 = p1; |
| 144 |
p1 += 3; |
| 145 |
} |
| 146 |
return(ncross & 01); |
| 147 |
} |
