ptrude/: changed extrusion from xy path to xz path; variable number of faces

ptrude/extrude.c

@@ -20,104 +20,85 @@
 
 
 #include <stdlib.h>
-#include <string.h>
 #include <math.h>
 
 #include "path.h"
 #include "extrude.h"
 
 
-#define	alloc_tn(t, n)	((t *) malloc(sizeof(t)*(n)))
-
-
-static void slice(double x, double y, double nx, double ny,
-    const struct path *shape, struct point *p)
+static void cvt_3d(struct point *p, const struct vertex *v, double z)
 {
-	const struct vertex *v;
-
-	for (v = shape->vertices; v; v = v->next) {
-		p->x = x+nx*v->x;
-		p->y = y+ny*v->x;
-		p->z = v->y;
-		p++;
-	}
+	p->x = v->x;
+	p->y = v->y;
+	p->z = z;
 }
 
 
-static void mesh(const struct point *a, const struct point *b, int n,
+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),
     void *data)
 {
-	int i;
+	const struct vertex *a = pa->vertices;
+	const struct vertex *b = pb->vertices;
+	double sa = 0, sb = 0;	/* total distance traveled on path */
+	double da, db;
+	struct point a3, b3, n;
 
-	for (i = 0; i != n-1; i++) {
-		face(data, a[i], b[i], a[i+1]);
-		face(data, a[i+1], b[i], b[i+1]);
+	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);
+		if ((a->next && da < db) || !b->next) {
+			cvt_3d(&n, a->next, za);
+			face(data, a3, n, b3);
+			a3 = n;
+			sa += a->len;
+			a = a->next;
+		} else {
+			cvt_3d(&n, b->next, zb);
+			face(data, b3, a3, n);
+			b3 = n;
+			sb += b->len;
+			b = b->next;
+		}
 	}
 }
 
 
 void extrude(const struct path *path, const struct path *shape,
+    double r, double d,
     void (*face)(void *data, struct point a, struct point b, struct point c),
     void *data)
 {
-	const struct vertex *v;		/* current vertex (for iteration) */
-	const struct vertex *a, *b, *c;	/* previous, current, next vertex */
-	struct point *prev, *this;	/* previous and current slice */
-	double nx, ny;			/* 2D normals */
-	double f;			/* factor for normalization */
-	double tx, ty;			/* temporary 2D normals */
-	int n = 0;			/* number of vertices in shape */
+	const struct vertex *v, *next;	/* current and next vertex */
+	struct path *prev, *curr;	/* previous and current path */
+	struct path *tmp;
 
-	if (!path->vertices || !path->vertices->next || !shape->vertices)
+	if (!path->vertices || !path->vertices->next)
 		return;
 
-	for (v = shape->vertices; v; v = v->next)
-		n++;
+	v = shape->vertices;
+	if (!v || !v->next)
+		return;
 
-	prev = alloc_tn(struct point, n);
-	this = alloc_tn(struct point, n);
+	tmp = stretch_path(path, v->x);
+	prev = round_path(tmp, r, d);
+	free_path(tmp);
 
-	a = path->vertices;
-	b = a->next;
-	nx = b->y-a->y;
-	ny = a->x-b->x;
-	f = hypot(nx, ny);
-	slice(a->x, a->y, nx/f, ny/f, shape, prev);
+	while (v->next) {
+		next = v->next;
+		tmp = stretch_path(path, next->x);
+		curr = round_path(tmp, r, d);
+		free_path(tmp);
 
-	for (v = path->vertices->next; v->next; v = v->next) {
-		b = v;
-		c = v->next;
+		mesh(prev, v->y, curr, next->y, face, data);
 
-		tx = b->y-a->y;
-		ty = a->x-b->x;
-		f = hypot(tx, ty);
-		nx = tx/f;
-		ny = ty/f;
-
-		tx = c->y-b->y;
-		ty = b->x-c->x;
-		f = hypot(tx, ty);
-		nx += tx/f;
-		ny += ty/f;
-
-		slice(b->x, b->y, nx/2, ny/2, shape, this);
-		mesh(prev, this, n, face, data);
-
-		memcpy(prev, this, sizeof(*prev)*n);
-
-		a = v;
+		free_path(prev);
+		prev = curr;
+		v = next;
 	}
 
-	nx = v->y-a->y;
-	ny = a->x-v->x;
-	f = hypot(nx, ny);
-
-	slice(v->x, v->y, nx/f, ny/f, shape, this);
-	mesh(prev, this, n, face, data);
-
-	/* @@@ To do: close shape and close top and bottom */
-
-	free(prev);
-	free(this);
+	free_path(prev);
 }

ptrude/extrude.h

@@ -0,0 +1,26 @@
+/*
+ * extrude.h - Perform the extrusion
+ *
+ * Written 2011 by Werner Almesberger
+ * Copyright 2011 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef EXTRUDE_H
+#define	EXTRUDE_H
+
+struct point {
+	double x, y, z;
+};
+
+
+void extrude(const struct path *path, const struct path *shape,
+    double r, double d,
+    void (*face)(void *data, struct point a, struct point b, struct point c),
+    void *data);
+
+#endif /* !EXTRUDE_H */

ptrude/ptrude.c

@@ -64,12 +64,13 @@ static void do_face(void *data, struct point a, struct point b, struct point c)
 }
 
 
-static void do_extrude(const struct path *path, const struct path *shape)
+static void do_extrude(const struct path *path, const struct path *shape,
+    double r, double d)
 {
 	FILE *file = stdout;
 
 	fprintf(file, "solid ptrude\n");
-	extrude(path, shape, do_face, file);
+	extrude(path, shape, r, d, do_face, file);
 	fprintf(file, "endsolid ptrude\n");
 }
 
@@ -87,7 +88,8 @@ static void usage(const char *name)
 int main(int argc, char **argv)
 {
 	FILE *file;
-	const struct path *path = NULL, *shape;
+	struct path *path = NULL;
+	const struct path *shape;
 	double r, d;
 	char *end;
 	int c;
@@ -128,9 +130,9 @@ int main(int argc, char **argv)
 		/*
 		 * We split the error budget evenly between path and shape.
 		 */
-		path = round_path(path, r, sqrt(d));
+		path_set_length(path);
 		shape = round_path(shape, r, sqrt(d));
-		do_extrude(path, shape);
+		do_extrude(path, shape, r, sqrt(d));
 	} else {
 		shape = round_path(shape, r, d);
 		save_path(stdout, shape);