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#ifndef lint
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static const char RCSid[] = "$Id: objtriangulate.c,v 2.1 2021/03/12 03:59:25 greg Exp $";
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#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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int rev;
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} 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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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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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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mysf.rev = (polyArea(poly) < .0);
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i = polyTriangulate(poly, addtriangle);
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polyFree(poly);
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/* flag face if replaced */
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f->flags |= (i > 0)*FACE_DUPLICATE;
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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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}
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