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ptrude/: many major math fixes, especially in stretch_path
This commit is contained in:
Werner Almesberger
parent
ee634458dc
commit
26a0f4cf2b
@ -44,6 +44,9 @@ $(MAIN): $(OBJS)
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try: $(MAIN)
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./$(MAIN) -d try 1 0.1 | tee out
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t2: $(MAIN)
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./$(MAIN) tp ts 25 0.1 >out.stl
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clean:
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rm -f $(OBJS) $(OBJS:.o=.d)
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@ -14,14 +14,14 @@
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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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* - the rounding is only accurate for x = 0. For x > 0, we need to add
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* more points. Tricky.
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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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@ -34,6 +34,26 @@ static void cvt_3d(struct point *p, const struct vertex *v, double 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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@ -47,6 +67,7 @@ static void mesh(const struct path *pa, double za,
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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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@ -83,14 +104,18 @@ void extrude(const struct path *path, const struct path *shape,
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if (!v || !v->next)
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return;
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tmp = stretch_path(path, v->x);
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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);
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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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@ -14,6 +14,7 @@
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#include <stdio.h>
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#include <string.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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@ -127,14 +128,16 @@ static void adjust_length(struct vertex *from, struct vertex *to, double len)
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struct vertex *v;
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double sum, f;
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if (from == to)
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return;
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sum = 0;
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for (v = from; v != to; v = v->next) {
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for (v = from->next; v != to; v = v->next) {
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v->len = hypot(v->x-v->next->x, v->y-v->next->y);
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sum += v->len;
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}
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f = len/sum;
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for (v = from; v != to; v = v->next)
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for (v = from->next; v != to; v = v->next)
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v->len *= f;
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}
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@ -178,6 +181,7 @@ static struct vertex *corner(struct path *path, struct vertex *a,
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int n; /* number of connecting segments (0 if none) */
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double f; /* scale factor; various uses */
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double fa, fb; /* scale factors for first and last vertex */
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double ang; /* current angle, for iteration */
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double x, y; /* current position; for iteration */
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int i; /* segment; for iteration */
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@ -226,15 +230,21 @@ static struct vertex *corner(struct path *path, struct vertex *a,
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* available length in half, one for the inbound arc, the other for the
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* outbound arc.
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*/
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/*
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* @@@ Our error checking is a bit overzealous and doesn't provide
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* enough information to debug any problems. Turn errors into warnings
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* for now.
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*/
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if (aa/2 < s) {
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fprintf(stderr, "first vector is too short (%g/2 < %g)\n",
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aa, s);
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exit(1);
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// exit(1);
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}
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if (bb/2 < s) {
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fprintf(stderr, "second vector is too short (%g/2 < %g)\n",
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bb, s);
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exit(1);
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// exit(1);
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}
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/*
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@ -279,11 +289,11 @@ static struct vertex *corner(struct path *path, struct vertex *a,
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* Step 4: emit the starting point of the arc
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*/
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f = s/aa;
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x = b->x-f*ax;
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y = b->y-f*ay;
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fa = s/aa;
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x = b->x-fa*ax;
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y = b->y-fa*ay;
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v0 = add_vertex(path, x, y, b->r, b->d, b->tag);
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a->len = a->len-s;
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v0->len = a->len*(1-fa);
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/*
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* Step 5: determine if we need intermediate points. If yes, how many,
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@ -337,15 +347,15 @@ static struct vertex *corner(struct path *path, struct vertex *a,
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* Step 6: emit the finishing point of the arc
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*/
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f = s/bb;
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v1 = add_vertex(path, b->x+f*bx, b->y+f*by, 0, 0, NULL);
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v1->len = b->len-s;
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fb = s/bb;
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v1 = add_vertex(path, b->x+fb*bx, b->y+fb*by, 0, 0, NULL);
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v1->len = b->len*(1-fb);
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/*
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* Step 7: adjust the nominal length of the segments
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*/
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adjust_length(v0, v1, 2*s);
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adjust_length(v0, v1, a->len*fa+b->len*fb);
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return v1;
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@ -386,18 +396,19 @@ struct path *round_path(const struct path *path, double r, double d)
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static void move_vertex(struct path *path, const struct vertex *v,
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double nx, double ny, double d)
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double nx, double ny, double dist, double r)
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{
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struct vertex *new;
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new = clone_vertex(v);
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new->x += nx*d;
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new->y += ny*d;
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new->x += nx*dist;
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new->y += ny*dist;
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new->r = r;
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append_vertex(path, new);
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}
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struct path *stretch_path(const struct path *path, double d)
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struct path *stretch_path(const struct path *path, double dist, double r)
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{
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struct path *new; /* new path */
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const struct vertex *v; /* current vertex (for iteration) */
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@ -413,9 +424,13 @@ struct path *stretch_path(const struct path *path, double d)
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nx = b->y-a->y;
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ny = a->x-b->x;
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f = hypot(nx, ny);
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move_vertex(new, a, nx/f, ny/f, d);
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if (a->r)
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r = a->r;
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move_vertex(new, a, nx/f, ny/f, dist, r);
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for (v = path->vertices->next; v->next; v = v->next) {
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double tmp;
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b = v;
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c = v->next;
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@ -425,12 +440,40 @@ struct path *stretch_path(const struct path *path, double d)
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nx = tx/f;
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ny = ty/f;
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tmp = f;
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tx = c->y-b->y;
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ty = b->x-c->x;
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f = hypot(tx, ty);
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nx += tx/f;
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ny += ty/f;
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move_vertex(new, b, nx/2, ny/2, d);
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if (b->r)
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r = b->r;
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f = hypot(nx, ny);
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nx /= f;
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ny /= f;
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/*
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* We have this far:
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* nx, ny = normal on corner, normalized
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* tmp = |a|, length of vector "a" (A -> B)
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* dist = the distance by which we stretch
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*
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* As shown in stretch.fig, we the length we need is
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* d' = d/cos(90-t)
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*
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* With
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* http://en.wikipedia.org/wiki/Trigonometric_identities#Symmetry
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* cos(90-t) = sin t = (n x a)/(|n|*|a|)
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*
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* Thus
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* d' = d/sin(t) - d*(|n|*|a|)/(n x a)
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* = d/sin(t) - d*|a|/(n x a)
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*/
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tmp = dist*tmp/(nx*(b->y-a->y)-ny*(b->x-a->x));
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move_vertex(new, b, nx, ny, tmp, r+dist);
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a = v;
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}
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@ -438,7 +481,9 @@ struct path *stretch_path(const struct path *path, double d)
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nx = v->y-a->y;
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ny = a->x-v->x;
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f = hypot(nx, ny);
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move_vertex(new, v, nx/f, ny/f, d);
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if (v->r)
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r = v->r;
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move_vertex(new, v, nx/f, ny/f, dist, r);
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return new;
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}
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@ -485,6 +530,7 @@ struct path *load_path(FILE *file)
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tag = NULL;
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}
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path_set_length(path);
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return path;
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}
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@ -42,7 +42,7 @@ void free_path(struct path *path);
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double path_set_length(struct path *path);
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struct path *round_path(const struct path *path, double r, double d);
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struct path *stretch_path(const struct path *path, double d);
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struct path *stretch_path(const struct path *path, double dist, double r);
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struct path *load_path(FILE *file);
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void save_path(FILE *file, const struct path *path);
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62
ptrude/stretch.fig
Normal file
62
ptrude/stretch.fig
Normal file
@ -0,0 +1,62 @@
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#FIG 3.2 Produced by xfig version 3.2.5b
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Landscape
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Center
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Metric
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A4
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100.00
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Single
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-2
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1200 2
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5 1 0 1 0 7 50 -1 -1 0.000 0 1 0 0 4275.476 4948.766 4725 4770 4507 4524 4275 4465
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5 1 0 1 0 7 50 -1 -1 0.000 0 1 0 0 3184.134 5404.540 4275 5400 4160 4917 3912 4592
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5 1 0 1 0 7 50 -1 -1 0.000 0 1 0 0 3189.289 5402.777 8865 5400 8394 3139 7314 1504
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2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 1 0 2
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0 0 2.00 90.00 120.00
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4275 7875 4275 4950
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2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 1 0 2
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0 0 2.00 90.00 120.00
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4275 4950 2250 2925
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 1 0 2
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0 0 1.00 90.00 120.00
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5647 4927 6592 3982
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2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 1 0 2
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0 0 2.00 90.00 120.00
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4275 4950 6570 4005
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 7 1 0 2
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0 0 1.00 90.00 120.00
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4275 4950 5625 4950
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 7 1 0 2
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0 0 1.00 90.00 120.00
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4275 4950 5220 4005
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 7 1 0 2
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0 0 1.00 90.00 120.00
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5220 4005 6570 4005
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 1 0 2
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0 0 1.00 90.00 120.00
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4275 4950 4275 2475
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 1 1 2
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0 0 1.00 90.00 120.00
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0 0 1.00 90.00 120.00
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4320 5850 8820 5850
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2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 3
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8865 6705 8865 3060 7245 1440
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 1 1 2
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0 0 1.00 90.00 120.00
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0 0 1.00 90.00 120.00
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4365 4995 8775 3150
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2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
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3195 5310 3195 5490
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2 1 0 2 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
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3105 5400 3285 5400
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2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
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3195 5400 4275 5400
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4 1 0 50 -1 18 18 0.0000 4 150 165 4095 6570 a\001
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4 1 0 50 -1 18 18 0.0000 4 210 180 3465 3825 b\001
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4 1 0 50 -1 18 18 0.0000 4 150 330 4995 5220 na\001
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4 1 0 50 -1 18 18 0.0000 4 150 165 5490 4365 n\001
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4 1 0 50 -1 18 18 0.0000 4 210 345 4770 4230 nb\001
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4 1 0 50 -1 18 18 0.0000 4 195 90 4410 4770 t\001
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4 1 0 50 -1 18 18 0.0000 4 270 1455 7470 3330 d/cos(90-t)\001
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4 1 0 50 -1 18 18 0.0000 4 210 180 6525 5805 d\001
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4 0 0 50 -1 18 18 0.0000 4 270 4845 4950 7875 cos(90-t) = sin t = n x a (normalized)\001
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4 1 0 50 -1 18 18 0.0000 4 150 105 3735 5310 r\001
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