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greg |
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#ifndef lint |
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static const char RCSid[] = "$Id: objtriangulate.c,v 2.2 2021/04/19 19:40:03 greg Exp $"; |
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greg |
2.1 |
#endif |
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/* |
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* Turn all faces with > 3 sides to triangles in Wavefront .OBJ scene |
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*/ |
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#include "copyright.h" |
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#include <stdio.h> |
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#include <stdlib.h> |
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#include "rterror.h" |
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#include "objutil.h" |
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#include "triangulate.h" |
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typedef struct { |
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Scene *sc; |
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Face *f; |
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greg |
2.2 |
int rev; |
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greg |
2.1 |
} SceneFace; |
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/* Callback to create new triangle */ |
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static int |
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addtriangle(const Vert2_list *tp, int a, int b, int c) |
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{ |
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SceneFace *sf = (SceneFace *)tp->p; |
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Face *f = sf->f; |
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VNDX triv[3]; |
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2.2 |
if (sf->rev) { /* need to reverse triangle? */ |
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int t = a; |
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a = c; |
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c = t; |
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} |
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2.1 |
triv[0][0] = f->v[a].vid; |
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triv[0][1] = f->v[a].tid; |
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triv[0][2] = f->v[a].nid; |
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triv[1][0] = f->v[b].vid; |
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triv[1][1] = f->v[b].tid; |
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triv[1][2] = f->v[b].nid; |
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triv[2][0] = f->v[c].vid; |
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triv[2][1] = f->v[c].tid; |
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triv[2][2] = f->v[c].nid; |
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f = addFace(sf->sc, triv, 3); |
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if (f == NULL) |
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return(0); |
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f->flags |= sf->f->flags; |
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f->grp = sf->f->grp; |
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f->mat = sf->f->mat; |
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return(1); |
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} |
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/* Callback to convert face to triangles */ |
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static int |
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mktriangles(Scene *sc, Face *f, void *p) |
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{ |
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Normal nrm; |
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int i, ax, ay; |
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Vert2_list *poly; |
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SceneFace mysf; |
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if (f->nv <= 3) /* already a triangle? */ |
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return(0); |
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if (faceArea(sc, f, nrm) == 0) /* hidden degenerate? */ |
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return(0); |
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/* identify major axis from normal */ |
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i = (nrm[1]*nrm[1] > nrm[0]*nrm[0]); |
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if (nrm[2]*nrm[2] > nrm[i]*nrm[i]) i = 2; |
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ax = (i+1)%3; |
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ay = (i+2)%3; |
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/* assign 2-D vertices */ |
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poly = polyAlloc(f->nv); |
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if (poly == NULL) { |
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error(SYSTEM, "Out of memory in mktriangles"); |
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return(-1); |
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} |
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mysf.sc = sc; |
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mysf.f = f; |
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poly->p = &mysf; |
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for (i = 0; i < f->nv; i++) { |
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double *pt = sc->vert[f->v[i].vid].p; |
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poly->v[i].mX = pt[ax]; |
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poly->v[i].mY = pt[ay]; |
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} |
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greg |
2.2 |
mysf.rev = (polyArea(poly) < .0); |
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2.1 |
i = polyTriangulate(poly, addtriangle); |
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polyFree(poly); |
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2.3 |
if (i > 0) /* flag face */ |
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f->flags |= FACE_DUPLICATE; |
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else |
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f->flags |= FACE_DEGENERATE; |
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greg |
2.1 |
return(i); |
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} |
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/* Convert all faces with > 3 vertices to triangles */ |
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int |
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triangulateScene(Scene *sc) |
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{ |
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int orig_nfaces = sc->nfaces; |
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int nc = foreachFace(sc, mktriangles, |
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0, FACE_DUPLICATE|FACE_DEGENERATE, NULL); |
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if (nc < 0) /* bad (memory) error? */ |
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return(-1); |
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if (nc > 0) /* else remove faces we split up */ |
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deleteFaces(sc, FACE_DUPLICATE, 0); |
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return(sc->nfaces - orig_nfaces); |
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} |
