ptrude/: many major math fixes, especially in stretch_path

ptrude/extrude.c

@@ -14,14 +14,14 @@
  * Known bugs:
  *
  * - negative x coordinates in shape produce overlapping faces
- * - the rounding is only accurate for x = 0. For x > 0, we need to add
- *   more points. Tricky.
  */
 
 
 #include <stdlib.h>
 #include <math.h>
+#include <assert.h>
 
+#include "ptrude.h"
 #include "path.h"
 #include "extrude.h"
 
@@ -34,6 +34,26 @@ static void cvt_3d(struct point *p, const struct vertex *v, double z)
 }
 
 
+static void size(const struct path *p)
+{
+	const struct vertex *v, *next;
+	double s = 0, sl = 0;
+	int n = 0;
+
+	if (!debug)
+		return;
+	for (v = p->vertices; v; v = next) {
+		next = v->next;
+		if (next)
+			s += hypot(v->x-next->x, v->y-next->y);
+		sl += v->len;
+		n++;
+	}
+	fprintf(stderr, "%d virt %g real %g\n", n, sl, s);
+	
+}
+
+
 static void mesh(const struct path *pa, double za,
     const struct path *pb, double zb,
     void (*face)(void *data, struct point a, struct point b, struct point c),
@@ -47,6 +67,7 @@ static void mesh(const struct path *pa, double za,
 
 	cvt_3d(&a3, a, za);
 	cvt_3d(&b3, b, zb);
+
 	while (a->next || b->next) {
 		da = fabs(sa+a->len-sb);
 		db = fabs(sb+b->len-sa);
@@ -83,14 +104,18 @@ void extrude(const struct path *path, const struct path *shape,
 	if (!v || !v->next)
 		return;
 
-	tmp = stretch_path(path, v->x);
+	tmp = stretch_path(path, v->x, r);
+	size(tmp);
 	prev = round_path(tmp, r, d);
 	free_path(tmp);
+	size(prev);
 
 	while (v->next) {
 		next = v->next;
-		tmp = stretch_path(path, next->x);
+		tmp = stretch_path(path, next->x, r);
+		size(tmp);
 		curr = round_path(tmp, r, d);
+		size(curr);
 		free_path(tmp);
 
 		mesh(prev, v->y, curr, next->y, face, data);