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ptrude/: functions for path stretching and calculation of proportional length
This commit is contained in:
Werner Almesberger
parent
c202eda676
commit
7ef626988c
140
ptrude/path.c
140
ptrude/path.c
@ -49,6 +49,7 @@ static struct vertex *alloc_vertex(void)
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v->d = 0;
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v->tag = NULL;
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v->next = NULL;
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v->len = 0;
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return v;
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}
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@ -89,7 +90,7 @@ static void append_vertex(struct path *path, struct vertex *v)
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}
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static const struct vertex *add_vertex(struct path *path, double x, double y,
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static struct vertex *add_vertex(struct path *path, double x, double y,
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double r, double d, const char *tag)
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{
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struct vertex *v;
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@ -105,14 +106,47 @@ static const struct vertex *add_vertex(struct path *path, double x, double y,
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}
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double path_set_length(struct path *path)
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{
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struct vertex *v;
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double sum = 0;
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if (!path->vertices)
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return 0;
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for (v = path->vertices; v->next; 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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v->len = 0;
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return sum;
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}
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static void adjust_length(struct vertex *from, struct vertex *to, double len)
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{
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struct vertex *v;
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double sum, f;
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sum = 0;
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for (v = from; 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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v->len *= f;
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}
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/*
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* "corner" replaces a corner with a ploygon if the corner is too sharp to
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* be within distance "d" of the bend radius. This may change the point from
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* "corner" replaces a corner with a ploygon if the corner is too sharp to be
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* within distance "d" of the bend radius. This may change the point from
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* where we resume drawing (originally the corner point, "b"). "corner"
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* therefore returns the new end of the arc.
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*/
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static const struct vertex *corner(struct path *path, const struct vertex *a,
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static struct vertex *corner(struct path *path, struct vertex *a,
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const struct vertex *b, const struct vertex *c, double r, double d)
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{
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/* points to vectors */
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@ -148,6 +182,10 @@ static const struct vertex *corner(struct path *path, const struct vertex *a,
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double x, y; /* current position; for iteration */
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int i; /* segment; for iteration */
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struct vertex *v0; /* first vertex of arc */
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struct vertex *v1; /* last vertex of arc */
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/*
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* http://en.wikipedia.org/wiki/Dot_product
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* dp = a*b*cos 2t
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@ -203,8 +241,9 @@ static const struct vertex *corner(struct path *path, const struct vertex *a,
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* If the corner is already smooth enough, we just keep what we have.
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*/
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if (dd <= d) {
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append_vertex(path, clone_vertex(b));
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return b;
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v1 = clone_vertex(b);
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append_vertex(path, v1);
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return v1;
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}
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/* Step 1: determine the total angle (2*t) */
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@ -243,7 +282,8 @@ static const struct vertex *corner(struct path *path, const struct vertex *a,
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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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add_vertex(path, x, y, b->r, b->d, b->tag);
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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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/*
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* Step 5: determine if we need intermediate points. If yes, how many,
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@ -298,21 +338,34 @@ static const struct vertex *corner(struct path *path, const struct vertex *a,
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*/
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f = s/bb;
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return add_vertex(path, b->x+f*bx, b->y+f*by, 0, 0, NULL);
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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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/*
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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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return v1;
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}
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struct path *round_path(const struct path *path, double r, double d)
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{
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struct path *new;
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const struct vertex *prev, *v;
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struct vertex *prev;
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const struct vertex *v;
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new = alloc_path();
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prev = path->vertices;
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if (!prev)
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if (!path->vertices)
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return new;
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append_vertex(new, clone_vertex(prev));
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if (!prev->next)
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prev = clone_vertex(path->vertices);
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append_vertex(new, prev);
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if (!path->vertices->next)
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return new;
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if (prev->r)
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@ -320,7 +373,7 @@ struct path *round_path(const struct path *path, double r, double d)
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if (prev->d)
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d = prev->d;
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for (v = prev->next; v->next; v = v->next) {
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for (v = path->vertices->next; v->next; v = v->next) {
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if (v->r)
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r = v->r;
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if (v->d)
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@ -332,6 +385,65 @@ struct path *round_path(const struct path *path, double r, double d)
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}
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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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{
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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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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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{
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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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const struct vertex *a, *b, *c; /* previous, current, next vertex */
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double nx, ny; /* 2D normals */
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double f; /* factor for normalization */
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double tx, ty; /* temporary 2D normals */
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new = alloc_path();
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a = path->vertices;
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b = a->next;
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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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for (v = path->vertices->next; v->next; v = v->next) {
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b = v;
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c = v->next;
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tx = b->y-a->y;
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ty = a->x-b->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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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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a = v;
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}
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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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return new;
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}
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struct path *load_path(FILE *file)
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{
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struct path *path;
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@ -22,6 +22,14 @@ struct vertex {
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double d; /* max. distance of corner from ideal arc; 0 = prev */
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const char *tag;
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struct vertex *next;
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/*
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* "len" is set by path_set_len to the distance to the next vertex, or
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* 0 if this is the last vertex in the path. round_path adjusts "len"
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* such that it corresponds to the length of the same part of the
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* original path.
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*/
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double len;
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};
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struct path {
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@ -32,7 +40,9 @@ struct path {
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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 *load_path(FILE *file);
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void save_path(FILE *file, const struct path *path);
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