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#ifndef lint
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static const char RCSid[] = "$Id: tmesh.c,v 2.3 2003/06/26 00:58:09 schorsch Exp $";
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#endif
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/*
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* Compute and print barycentric coordinates for triangle meshes
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*/
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#include <stdio.h>
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#include "fvect.h"
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#include "tmesh.h"
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#define ABS(x) ((x) >= 0 ? (x) : -(x))
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int
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flat_tri(v1, v2, v3, n1, n2, n3) /* determine if triangle is flat */
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FVECT v1, v2, v3, n1, n2, n3;
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{
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double d1, d2, d3;
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FVECT vt1, vt2, vn;
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/* compute default normal */
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VSUB(vt1, v2, v1);
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VSUB(vt2, v3, v2);
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VCROSS(vn, vt1, vt2);
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if (normalize(vn) == 0.0)
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return(DEGEN);
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/* compare to supplied normals */
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d1 = DOT(vn, n1); d2 = DOT(vn, n2); d3 = DOT(vn, n3);
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if (d1 < 0 && d2 < 0 && d3 < 0) {
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if (d1 > -COSTOL || d2 > -COSTOL || d3 > -COSTOL)
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return(RVBENT);
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return(RVFLAT);
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}
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if (d1 < COSTOL || d2 < COSTOL || d3 < COSTOL)
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return(ISBENT);
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return(ISFLAT);
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}
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int
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comp_baryc(bcm, v1, v2, v3) /* compute barycentric vectors */
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register BARYCCM *bcm;
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RREAL *v1, *v2, *v3;
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{
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RREAL *vt;
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FVECT va, vab, vcb;
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double d;
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int ax0, ax1;
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register int i;
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/* compute major axis */
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VSUB(vab, v1, v2);
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VSUB(vcb, v3, v2);
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VCROSS(va, vab, vcb);
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bcm->ax = ABS(va[0]) > ABS(va[1]) ? 0 : 1;
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bcm->ax = ABS(va[bcm->ax]) > ABS(va[2]) ? bcm->ax : 2;
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ax0 = (bcm->ax + 1) % 3;
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ax1 = (bcm->ax + 2) % 3;
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for (i = 0; i < 2; i++) {
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vab[0] = v1[ax0] - v2[ax0];
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vcb[0] = v3[ax0] - v2[ax0];
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vab[1] = v1[ax1] - v2[ax1];
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vcb[1] = v3[ax1] - v2[ax1];
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d = vcb[0]*vcb[0] + vcb[1]*vcb[1];
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if (d <= FTINY*FTINY)
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return(-1);
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d = (vcb[0]*vab[0]+vcb[1]*vab[1])/d;
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va[0] = vab[0] - vcb[0]*d;
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va[1] = vab[1] - vcb[1]*d;
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d = va[0]*va[0] + va[1]*va[1];
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if (d <= FTINY*FTINY)
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return(-1);
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d = 1.0/d;
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bcm->tm[i][0] = va[0] *= d;
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bcm->tm[i][1] = va[1] *= d;
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bcm->tm[i][2] = -(v2[ax0]*va[0]+v2[ax1]*va[1]);
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/* rotate vertices */
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vt = v1;
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v1 = v2;
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v2 = v3;
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v3 = vt;
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}
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return(0);
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}
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void
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eval_baryc(wt, p, bcm) /* evaluate barycentric weights at p */
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RREAL wt[3];
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FVECT p;
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register BARYCCM *bcm;
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{
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double u, v;
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u = p[(bcm->ax + 1) % 3];
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v = p[(bcm->ax + 2) % 3];
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wt[0] = u*bcm->tm[0][0] + v*bcm->tm[0][1] + bcm->tm[0][2];
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wt[1] = u*bcm->tm[1][0] + v*bcm->tm[1][1] + bcm->tm[1][2];
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wt[2] = 1. - wt[1] - wt[0];
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}
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int
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get_baryc(wt, p, v1, v2, v3) /* compute barycentric weights at p */
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RREAL wt[3];
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FVECT p;
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FVECT v1, v2, v3;
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{
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BARYCCM bcm;
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if (comp_baryc(&bcm, v1, v2, v3) < 0)
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return(-1);
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eval_baryc(wt, p, &bcm);
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return(0);
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}
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#if 0
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int
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get_baryc(wt, p, v1, v2, v3) /* compute barycentric weights at p */
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RREAL wt[3];
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FVECT p;
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FVECT v1, v2, v3;
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{
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FVECT ac, bc, pc, cros;
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double normf;
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/* area formula w/o 2-D optimization */
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VSUB(ac, v1, v3);
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VSUB(bc, v2, v3);
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VSUB(pc, p, v3);
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VCROSS(cros, ac, bc);
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normf = DOT(cros,cros)
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if (normf <= 0.0)
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return(-1);
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normf = 1./sqrt(normf);
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VCROSS(cros, bc, pc);
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wt[0] = VLEN(cros) * normf;
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VCROSS(cros, ac, pc);
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wt[1] = VLEN(cros) * normf;
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wt[2] = 1. - wt[1] - wt[0];
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return(0);
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}
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#endif
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void
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put_baryc(bcm, com, n) /* put barycentric coord. vectors */
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register BARYCCM *bcm;
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register RREAL com[][3];
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int n;
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{
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double a, b;
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register int i;
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printf("%d\t%d\n", 1+3*n, bcm->ax);
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for (i = 0; i < n; i++) {
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a = com[i][0] - com[i][2];
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b = com[i][1] - com[i][2];
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printf("%14.8f %14.8f %14.8f\n",
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bcm->tm[0][0]*a + bcm->tm[1][0]*b,
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bcm->tm[0][1]*a + bcm->tm[1][1]*b,
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bcm->tm[0][2]*a + bcm->tm[1][2]*b + com[i][2]);
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}
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}
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