| 1 |
#ifndef lint |
| 2 |
static const char RCSid[] = "$Id: objtriangulate.c,v 2.2 2021/04/19 19:40:03 greg Exp $"; |
| 3 |
#endif |
| 4 |
/* |
| 5 |
* Turn all faces with > 3 sides to triangles in Wavefront .OBJ scene |
| 6 |
*/ |
| 7 |
|
| 8 |
#include "copyright.h" |
| 9 |
|
| 10 |
#include <stdio.h> |
| 11 |
#include <stdlib.h> |
| 12 |
#include "rterror.h" |
| 13 |
#include "objutil.h" |
| 14 |
#include "triangulate.h" |
| 15 |
|
| 16 |
typedef struct { |
| 17 |
Scene *sc; |
| 18 |
Face *f; |
| 19 |
int rev; |
| 20 |
} SceneFace; |
| 21 |
|
| 22 |
/* Callback to create new triangle */ |
| 23 |
static int |
| 24 |
addtriangle(const Vert2_list *tp, int a, int b, int c) |
| 25 |
{ |
| 26 |
SceneFace *sf = (SceneFace *)tp->p; |
| 27 |
Face *f = sf->f; |
| 28 |
VNDX triv[3]; |
| 29 |
|
| 30 |
if (sf->rev) { /* need to reverse triangle? */ |
| 31 |
int t = a; |
| 32 |
a = c; |
| 33 |
c = t; |
| 34 |
} |
| 35 |
triv[0][0] = f->v[a].vid; |
| 36 |
triv[0][1] = f->v[a].tid; |
| 37 |
triv[0][2] = f->v[a].nid; |
| 38 |
triv[1][0] = f->v[b].vid; |
| 39 |
triv[1][1] = f->v[b].tid; |
| 40 |
triv[1][2] = f->v[b].nid; |
| 41 |
triv[2][0] = f->v[c].vid; |
| 42 |
triv[2][1] = f->v[c].tid; |
| 43 |
triv[2][2] = f->v[c].nid; |
| 44 |
|
| 45 |
f = addFace(sf->sc, triv, 3); |
| 46 |
if (f == NULL) |
| 47 |
return(0); |
| 48 |
|
| 49 |
f->flags |= sf->f->flags; |
| 50 |
f->grp = sf->f->grp; |
| 51 |
f->mat = sf->f->mat; |
| 52 |
return(1); |
| 53 |
} |
| 54 |
|
| 55 |
/* Callback to convert face to triangles */ |
| 56 |
static int |
| 57 |
mktriangles(Scene *sc, Face *f, void *p) |
| 58 |
{ |
| 59 |
Normal nrm; |
| 60 |
int i, ax, ay; |
| 61 |
Vert2_list *poly; |
| 62 |
SceneFace mysf; |
| 63 |
|
| 64 |
if (f->nv <= 3) /* already a triangle? */ |
| 65 |
return(0); |
| 66 |
|
| 67 |
if (faceArea(sc, f, nrm) == 0) /* hidden degenerate? */ |
| 68 |
return(0); |
| 69 |
/* identify major axis from normal */ |
| 70 |
i = (nrm[1]*nrm[1] > nrm[0]*nrm[0]); |
| 71 |
if (nrm[2]*nrm[2] > nrm[i]*nrm[i]) i = 2; |
| 72 |
ax = (i+1)%3; |
| 73 |
ay = (i+2)%3; |
| 74 |
/* assign 2-D vertices */ |
| 75 |
poly = polyAlloc(f->nv); |
| 76 |
if (poly == NULL) { |
| 77 |
error(SYSTEM, "Out of memory in mktriangles"); |
| 78 |
return(-1); |
| 79 |
} |
| 80 |
mysf.sc = sc; |
| 81 |
mysf.f = f; |
| 82 |
poly->p = &mysf; |
| 83 |
for (i = 0; i < f->nv; i++) { |
| 84 |
double *pt = sc->vert[f->v[i].vid].p; |
| 85 |
poly->v[i].mX = pt[ax]; |
| 86 |
poly->v[i].mY = pt[ay]; |
| 87 |
} |
| 88 |
mysf.rev = (polyArea(poly) < .0); |
| 89 |
i = polyTriangulate(poly, addtriangle); |
| 90 |
polyFree(poly); |
| 91 |
if (i > 0) /* flag face */ |
| 92 |
f->flags |= FACE_DUPLICATE; |
| 93 |
else |
| 94 |
f->flags |= FACE_DEGENERATE; |
| 95 |
return(i); |
| 96 |
} |
| 97 |
|
| 98 |
/* Convert all faces with > 3 vertices to triangles */ |
| 99 |
int |
| 100 |
triangulateScene(Scene *sc) |
| 101 |
{ |
| 102 |
int orig_nfaces = sc->nfaces; |
| 103 |
int nc = foreachFace(sc, mktriangles, |
| 104 |
0, FACE_DUPLICATE|FACE_DEGENERATE, NULL); |
| 105 |
|
| 106 |
if (nc < 0) /* bad (memory) error? */ |
| 107 |
return(-1); |
| 108 |
if (nc > 0) /* else remove faces we split up */ |
| 109 |
deleteFaces(sc, FACE_DUPLICATE, 0); |
| 110 |
|
| 111 |
return(sc->nfaces - orig_nfaces); |
| 112 |
} |
