Root/slicer/slice.c

1/*
2 * slice.c - Generate slices
3 *
4 * Written 2015 by Werner Almesberger
5 * Copyright 2015 by Werner Almesberger
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 */
12
13
14#include <stdbool.h>
15#include <math.h>
16#include <glib.h>
17
18#include "util.h"
19#include "stl.h"
20#include "slice.h"
21
22
23struct facet {
24    struct v a, b, c;
25    struct facet *next;
26};
27
28
29struct z {
30    float z;
31};
32
33
34static GTree *tree;
35static struct facet *facets = NULL;
36
37
38/* ----- Bounding box ------------------------------------------------------ */
39
40
41static bool first = 1;
42static float min_x, max_x, min_y, max_y;
43
44
45static void bbox(float x, float y)
46{
47    if (first) {
48        min_x = max_x = x;
49        min_y = max_y = y;
50        first = 0;
51    } else {
52        if (x < min_x)
53            min_x = x;
54        if (y < min_y)
55            min_y = y;
56        if (x > max_x)
57            max_x = x;
58        if (y > max_y)
59            max_y = y;
60    }
61}
62
63
64/* ----- Data collection --------------------------------------------------- */
65
66
67static inline bool eq(float a, float b)
68{
69    return fabsf(a - b) < 1e-5;
70}
71
72
73static void mark_z(float z)
74{
75    struct z *e;
76
77    e = g_tree_lookup(tree, &z);
78    if (e)
79        return;
80    e = alloc_type(struct z);
81    e->z = z;
82    g_tree_insert(tree, &e->z, e);
83}
84
85
86static void add(const struct v *a, const struct v *b, const struct v *c)
87{
88    float cross;
89    struct facet *f;
90
91    cross = (b->x - a->x) * (c->y - a->y) - (b->y - a->y) * (c->x - a->x);
92    if (!eq(cross, 0)) {
93        fprintf(stderr,
94            "inclined facet\n\t%f %f %f\n\t%f %f %f\n\t%f %f %f\n",
95            a->x, a->y, a->z, b->x, b->y, b->z, c->x, c->y, c->z);
96        exit(1);
97    }
98
99    bbox(a->x, a->y);
100    bbox(b->x, b->y);
101    bbox(c->x, c->y);
102
103    f = alloc_type(struct facet);
104    f->a = *a;
105    f->b = *b;
106    f->c = *c;
107    f->next = facets;
108    facets = f;
109}
110
111
112void slice(struct v f[3])
113{
114    bool ab = eq(f[0].z, f[1].z);
115    bool bc = eq(f[1].z, f[2].z);
116
117    if (ab && bc) {
118        mark_z(f[0].z);
119        return;
120    }
121    add(f + 0, f + 1, f + 2);
122}
123
124
125/* ----- Insert intermediate layers ---------------------------------------- */
126
127
128struct ctx {
129    float z_step;
130    bool first;
131    float z0; /* only defined if !first */
132    bool more; /* returned due to having made changes */
133};
134
135
136static gboolean check_z(gpointer key, gpointer value, gpointer data)
137{
138    const struct z *z = value;
139    struct ctx *ctx = data;
140    float d;
141    int n, i;
142
143    if (ctx->first) {
144        ctx->first = 0;
145        ctx->z0 = z->z;
146        return 0;
147    }
148
149    d = z->z - ctx->z0;
150    if (d <= ctx->z_step) {
151        ctx->z0 = z->z;
152        return 0;
153    }
154
155    n = (d / ctx->z_step) + 1;
156    for (i = 1; i < n; i++)
157        mark_z(ctx->z0 + d / n * i);
158
159    ctx->more = 1;
160    return 1;
161}
162
163
164void slice_intermediate(float z_step)
165{
166    struct ctx ctx = {
167        .z_step = z_step,
168    };
169
170    do {
171        ctx.first = 1;
172        ctx.more = 0;
173        g_tree_foreach(tree, check_z, &ctx);
174    }
175    while (ctx.more);
176}
177
178
179/* ----- Dumping ----------------------------------------------------------- */
180
181
182static bool cut(const struct v *a, const struct v *b, float z, struct v *res)
183{
184    float dx, dy, dz;
185    float f;
186
187    if (a->z > b->z)
188        return cut(b, a, z, res);
189    if (eq(a->z, b->z))
190        return 0;
191    if (a->z > z || b->z < z || eq(b->z, z))
192        return 0;
193
194    dx = b->x - a->x;
195    dy = b->y - a->y;
196    dz = b->z - a->z;
197
198    f = (z - a->z) / dz;
199
200    res->x = f * dx + a->x;
201    res->y = f * dy + a->y;
202    res->z = z;
203
204    return 1;
205}
206
207
208static gboolean dump_layer(gpointer key, gpointer value, gpointer data)
209{
210    const struct z *z = value;
211    const struct facet *f;
212    struct v p1, p2;
213
214    for (f = facets; f; f = f->next) {
215        if (cut(&f->a, &f->b, z->z, &p1)) {
216            if (!cut(&f->a, &f->c, z->z, &p2) &&
217                !cut(&f->b, &f->c, z->z, &p2))
218                continue;
219        } else if (!cut(&f->a, &f->c, z->z, &p1) ||
220            !cut(&f->b, &f->c, z->z, &p2)) {
221            continue;
222        }
223        printf("%f %f %f\n%f %f %f\n\n\n",
224            p1.x, p1.y, z->z, p2.x, p2.y, z->z);
225
226    }
227    return 0;
228}
229
230
231static gboolean dump_box(gpointer key, gpointer value, gpointer data)
232{
233    const struct z *z = value;
234    float box = *(float *) data;
235
236    printf("%f %f %f\n%f %f %f\n%f %f %f\n%f %f %f\n%f %f %f\n\n\n",
237        min_x - box, min_y - box, z->z,
238        max_x + box, min_y - box, z->z,
239        max_x + box, max_y + box, z->z,
240        min_x - box, max_y + box, z->z,
241        min_x - box, min_y - box, z->z);
242    
243    return 0;
244}
245
246
247void slice_dump(float box)
248{
249    g_tree_foreach(tree, dump_layer, NULL);
250    if (box && !first)
251        g_tree_foreach(tree, dump_box, &box);
252}
253
254
255/* ----- Initialization ---------------------------------------------------- */
256
257
258static gint comp(gconstpointer a, gconstpointer b)
259{
260    const float *za = a;
261    const float *zb = b;
262
263    return eq(*za, *zb) ? 0 : *za < *zb ? -1 : 1;
264}
265
266
267void slice_init(void)
268{
269    tree = g_tree_new(comp);
270}
271

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