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greg |
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/*
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#ifndef lint
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static char SCCSid[] = "$SunId$ LBL";
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#endif
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* gensurf.c - program to generate functional surfaces
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*
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* Parametric functions x(s,t), y(s,t) and z(s,t)
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* specify the surface, which is tesselated into an m by n
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* array of paired triangles.
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* The surface normal is defined by the right hand
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* rule applied to (s,t).
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*
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* 4/3/87
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*/
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#include <stdio.h>
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#define XNAME "X_" /* x function name */
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#define YNAME "Y_" /* y function name */
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#define ZNAME "Z_" /* z function name */
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#define PI 3.14159265358979323846
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#define FTINY 1e-7
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#define vertex(p) printf(vformat, (p)[0], (p)[1], (p)[2])
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char vformat[] = "%15.9g %15.9g %15.9g\n";
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double funvalue(), dist2(), fdot(), l_hermite(), argument();
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main(argc, argv)
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int argc;
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char *argv[];
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{
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static double *xyz[4];
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double *row0, *row1, *dp;
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double v1[3], v2[3], vc1[3], vc2[3];
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double a1, a2;
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int i, j, m, n;
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char stmp[256];
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double d;
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register int k;
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varset("PI", PI);
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funset("hermite", 5, l_hermite);
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if (argc < 8)
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goto userror;
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for (i = 8; i < argc; i++)
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if (!strcmp(argv[i], "-e"))
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scompile(NULL, argv[++i]);
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else if (!strcmp(argv[i], "-f"))
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fcompile(argv[++i]);
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else
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goto userror;
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sprintf(stmp, "%s(s,t)=%s;", XNAME, argv[3]);
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scompile(NULL, stmp);
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sprintf(stmp, "%s(s,t)=%s;", YNAME, argv[4]);
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scompile(NULL, stmp);
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sprintf(stmp, "%s(s,t)=%s;", ZNAME, argv[5]);
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scompile(NULL, stmp);
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m = atoi(argv[6]);
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n = atoi(argv[7]);
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if (m <= 0 || n <= 0)
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goto userror;
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row0 = (double *)malloc((n+1)*3*sizeof(double));
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row1 = (double *)malloc((n+1)*3*sizeof(double));
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if (row0 == NULL || row1 == NULL) {
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fprintf(stderr, "%s: out of memory\n", argv[0]);
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quit(1);
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}
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printhead(argc, argv);
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comprow(0.0, row1, n); /* compute zeroeth row */
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for (i = 0; i < m; i++) {
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/* compute next row */
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dp = row0;
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row0 = row1;
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row1 = dp;
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comprow((double)(i+1)/m, row1, n);
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for (j = 0; j < n; j++) {
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/* get vertices */
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xyz[0] = row0 + 3*j;
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xyz[1] = row1 + 3*j;
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xyz[2] = xyz[0] + 3;
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xyz[3] = xyz[1] + 3;
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/* rotate vertices */
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if (dist2(xyz[0],xyz[3]) < dist2(xyz[1],xyz[2])-FTINY) {
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dp = xyz[0];
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xyz[0] = xyz[1];
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xyz[1] = xyz[3];
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xyz[3] = xyz[2];
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xyz[2] = dp;
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}
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/* get normals */
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for (k = 0; k < 3; k++) {
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v1[k] = xyz[1][k] - xyz[0][k];
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v2[k] = xyz[2][k] - xyz[0][k];
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}
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fcross(vc1, v1, v2);
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a1 = fdot(vc1, vc1);
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for (k = 0; k < 3; k++) {
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v1[k] = xyz[2][k] - xyz[3][k];
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v2[k] = xyz[1][k] - xyz[3][k];
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}
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fcross(vc2, v1, v2);
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a2 = fdot(vc2, vc2);
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/* check coplanar */
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if (a1 > FTINY*FTINY && a2 > FTINY*FTINY) {
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d = fdot(vc1, vc2);
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if (d*d/a1/a2 >= 1.0-FTINY*FTINY) {
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if (d > 0.0) { /* coplanar */
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printf(
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"\n%s polygon %s.%d.%d\n",
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argv[1], argv[2], i+1, j+1);
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printf("0\n0\n12\n");
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vertex(xyz[0]);
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vertex(xyz[1]);
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vertex(xyz[3]);
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vertex(xyz[2]);
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} /* else overlapped */
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continue;
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} /* else bent */
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}
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/* check triangles */
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if (a1 > FTINY*FTINY) {
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printf("\n%s polygon %s.%da%d\n",
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argv[1], argv[2], i+1, j+1);
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printf("0\n0\n9\n");
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vertex(xyz[0]);
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vertex(xyz[1]);
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vertex(xyz[2]);
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}
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if (a2 > FTINY*FTINY) {
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printf("\n%s polygon %s.%db%d\n",
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argv[1], argv[2], i+1, j+1);
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printf("0\n0\n9\n");
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vertex(xyz[2]);
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vertex(xyz[1]);
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vertex(xyz[3]);
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}
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}
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}
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quit(0);
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userror:
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fprintf(stderr, "Usage: %s material name ", argv[0]);
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fprintf(stderr, "x(s,t) y(s,t) z(s,t) m n [-e expr] [-f file]\n");
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quit(1);
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}
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comprow(s, row, siz) /* compute row of values */
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double s;
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register double *row;
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int siz;
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{
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double st[2], step;
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st[0] = s;
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st[1] = 0.0;
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step = 1.0 / siz;
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while (siz-- >= 0) {
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*row++ = funvalue(XNAME, 2, st);
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*row++ = funvalue(YNAME, 2, st);
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*row++ = funvalue(ZNAME, 2, st);
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st[1] += step;
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}
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}
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eputs(msg)
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char *msg;
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{
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fputs(msg, stderr);
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}
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wputs(msg)
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char *msg;
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{
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eputs(msg);
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}
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quit(code)
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{
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exit(code);
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}
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printhead(ac, av) /* print command header */
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register int ac;
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register char **av;
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{
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putchar('#');
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while (ac--) {
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putchar(' ');
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fputs(*av++, stdout);
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}
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putchar('\n');
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}
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double
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l_hermite()
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{
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double t;
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t = argument(5);
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return( argument(1)*((2.0*t-3.0)*t*t+1.0) +
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argument(2)*(-2.0*t+3.0)*t*t +
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argument(3)*((t-2.0)*t+1.0)*t +
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argument(4)*(t-1.0)*t*t );
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}
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