130 lines
2.5 KiB
C
130 lines
2.5 KiB
C
/*
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* extrude.c - Perform the extrusion
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*
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* Written 2011 by Werner Almesberger
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* Copyright 2011 by Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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/*
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* Known bugs:
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*
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* - negative x coordinates in shape produce overlapping faces
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*/
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#include <stdlib.h>
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#include <math.h>
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#include <assert.h>
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#include "ptrude.h"
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#include "path.h"
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#include "extrude.h"
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static void cvt_3d(struct point *p, const struct vertex *v, double z)
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{
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p->x = v->x;
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p->y = v->y;
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p->z = z;
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}
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static void size(const struct path *p)
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{
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const struct vertex *v, *next;
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double s = 0, sl = 0;
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int n = 0;
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if (!debug)
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return;
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for (v = p->vertices; v; v = next) {
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next = v->next;
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if (next)
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s += hypot(v->x-next->x, v->y-next->y);
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sl += v->len;
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n++;
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}
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fprintf(stderr, "%d virt %g real %g\n", n, sl, s);
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}
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static void mesh(const struct path *pa, double za,
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const struct path *pb, double zb,
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void (*face)(void *data, struct point a, struct point b, struct point c),
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void *data)
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{
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const struct vertex *a = pa->vertices;
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const struct vertex *b = pb->vertices;
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double sa = 0, sb = 0; /* total distance traveled on path */
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double da, db;
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struct point a3, b3, n;
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cvt_3d(&a3, a, za);
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cvt_3d(&b3, b, zb);
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while (a->next || b->next) {
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da = fabs(sa+a->len-sb);
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db = fabs(sb+b->len-sa);
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if ((a->next && da < db) || !b->next) {
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cvt_3d(&n, a->next, za);
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face(data, a3, n, b3);
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a3 = n;
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sa += a->len;
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a = a->next;
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} else {
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cvt_3d(&n, b->next, zb);
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face(data, b3, a3, n);
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b3 = n;
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sb += b->len;
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b = b->next;
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}
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}
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}
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void extrude(const struct path *path, const struct path *shape,
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double r, double d,
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void (*face)(void *data, struct point a, struct point b, struct point c),
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void *data)
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{
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const struct vertex *v, *next; /* current and next vertex */
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struct path *prev, *curr; /* previous and current path */
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struct path *tmp;
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if (!path->vertices || !path->vertices->next)
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return;
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v = shape->vertices;
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if (!v || !v->next)
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return;
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tmp = stretch_path(path, v->x, r);
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size(tmp);
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prev = round_path(tmp, r, d);
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free_path(tmp);
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size(prev);
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while (v->next) {
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next = v->next;
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tmp = stretch_path(path, next->x, r);
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size(tmp);
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curr = round_path(tmp, r, d);
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size(curr);
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free_path(tmp);
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mesh(prev, v->y, curr, next->y, face, data);
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free_path(prev);
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prev = curr;
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v = next;
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}
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free_path(prev);
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}
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