ptrude/: added (overly, this far) simple extruder

ptrude/Makefile

@@ -13,7 +13,7 @@
 SHELL = /bin/bash
 
 MAIN = ptrude
-OBJS = $(MAIN).o path.o
+OBJS = $(MAIN).o path.o extrude.o
 
 CFLAGS = -Wall -g -Wshadow -Wmissing-prototypes \
          -Wmissing-declarations -Wno-format-zero-length

ptrude/extrude.c

@@ -0,0 +1,123 @@
+/*
+ * extrude.c - 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.
+ */
+
+/*
+ * 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 <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)
+{
+	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++;
+	}
+}
+
+
+static void mesh(const struct point *a, const struct point *b, int n,
+    void (*face)(void *data, struct point a, struct point b, struct point c),
+    void *data)
+{
+	int i;
+
+	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]);
+	}
+}
+
+
+void extrude(const struct path *path, const struct path *shape,
+    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 */
+
+	if (!path->vertices || !path->vertices->next || !shape->vertices)
+		return;
+
+	for (v = shape->vertices; v; v = v->next)
+		n++;
+
+	prev = alloc_tn(struct point, n);
+	this = alloc_tn(struct point, n);
+
+	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);
+
+	for (v = path->vertices->next; v->next; v = v->next) {
+		b = v;
+		c = v->next;
+
+		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;
+	}
+
+	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);
+}

ptrude/mesh.fig

@@ -0,0 +1,65 @@
+#FIG 3.2  Produced by xfig version 3.2.5b
+Landscape
+Center
+Metric
+A4      
+100.00
+Single
+-2
+1200 2
+2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 2925 7200 4050 8325
+2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 2925 5400 4275 7200
+2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 2025 4500 4275 5400
+2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 3420 4500 6930 4050
+2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 6075 3150 8325 2025
+2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 4275 5400 6975 5850
+2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 6975 5850 8100 4950
+2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 4275 7200 6750 6975
+2 1 0 1 0 7 50 -1 -1 0.000 0 0 -1 0 0 2
+	 6975 4050 8280 3825
+2 1 0 3 1 7 50 -1 -1 0.000 0 0 -1 1 0 4
+	1 1 3.00 90.00 120.00
+	 2700 8325 2925 7200 2925 5400 2025 4500
+2 1 0 2 1 7 50 -1 -1 0.000 0 0 7 0 0 4
+	 4050 8325 4275 7200 4275 5400 3375 4500
+2 1 0 2 1 7 50 -1 -1 0.000 0 0 7 0 0 4
+	 6750 6975 6975 5850 6975 4050 6075 3150
+2 1 0 2 1 7 50 -1 -1 0.000 0 0 7 0 0 4
+	 8100 4950 8325 3825 8325 2025 7425 1125
+2 1 0 2 4 7 50 -1 -1 0.000 0 0 7 0 0 4
+	 2025 4500 3375 4500 6075 3150 7425 1125
+2 1 0 2 4 7 50 -1 -1 0.000 0 0 7 0 0 4
+	 2925 5400 4275 5400 6975 4050 8325 2025
+2 1 0 3 4 7 50 -1 -1 0.000 0 0 -1 1 0 4
+	1 1 3.00 90.00 120.00
+	 2925 7200 4275 7200 6975 5850 8325 3825
+2 1 0 2 4 7 50 -1 -1 0.000 0 0 7 0 0 4
+	 2709 8343 4059 8343 6759 6993 8109 4968
+2 1 0 2 4 7 52 -1 -1 0.000 0 0 -1 0 0 2
+	 3195 6975 3015 7155
+2 1 0 2 1 7 52 -1 -1 0.000 0 0 -1 0 0 2
+	 2520 7200 2790 7200
+2 1 0 2 1 7 52 -1 -1 0.000 0 0 -1 0 0 2
+	 2250 8505 2565 8370
+3 2 0 2 0 7 50 -1 -1 0.000 0 1 0 3
+	0 0 2.00 90.00 120.00
+	 4680 6705 5580 6075 4545 5805
+	 0.000 -1.000 0.000
+3 2 0 2 0 7 50 -1 -1 0.000 0 1 0 3
+	0 0 2.00 90.00 120.00
+	 5265 5265 6570 5445 6705 4545
+	 0.000 -1.000 0.000
+4 2 1 50 -1 18 18 0.0000 4 270 870 2835 6480 Shape\001
+4 1 4 50 -1 18 18 0.0000 4 210 615 3690 7515 Path\001
+4 1 4 50 -1 19 15 0.0000 4 240 375 3330 6930 tag\001
+4 1 1 50 -1 19 15 0.0000 4 240 375 2295 7245 tag\001
+4 1 1 50 -1 14 15 0.0000 4 135 750 1845 8640 start\001
+4 1 1 50 -1 18 12 0.0000 4 195 1365 2205 8865 (or unique tag)\001

ptrude/ptrude.c

@@ -17,6 +17,7 @@
 #include <math.h>
 
 #include "path.h"
+#include "extrude.h"
 #include "ptrude.h"
 
 
@@ -50,6 +51,29 @@ static void close_file(FILE *file)
 }
 
 
+static void do_face(void *data, struct point a, struct point b, struct point c)
+{
+	FILE *file = data;
+
+	fprintf(file, "facet normal 0 0 0\n");
+	fprintf(file, "  outer loop\n");
+	fprintf(file, "  vertex %f %f %f\n", a.x, a.y, a.z);
+	fprintf(file, "  vertex %f %f %f\n", b.x, b.y, b.z);
+	fprintf(file, "  vertex %f %f %f\n", c.x, c.y, c.z);
+	fprintf(file, "  endloop\nendfacet\n");
+}
+
+
+static void do_extrude(const struct path *path, const struct path *shape)
+{
+	FILE *file = stdout;
+
+	fprintf(file, "solid ptrude\n");
+	extrude(path, shape, do_face, file);
+	fprintf(file, "endsolid ptrude\n");
+}
+
+
 static void usage(const char *name)
 {
 	fprintf(stderr,
@@ -106,7 +130,7 @@ int main(int argc, char **argv)
 		 */
 		path = round_path(path, r, sqrt(d));
 		shape = round_path(shape, r, sqrt(d));
-		/* ... now all that's missing is the extrusion :-) */
+		do_extrude(path, shape);
 	} else {
 		shape = round_path(shape, r, d);
 		save_path(stdout, shape);

ptrude/tp

@@ -0,0 +1,10 @@
+# test path
+-100 0
+100 0
+200 100
+200 200
+100 300
+0 300
+-100 200
+-100 100
+0 100

ptrude/ts

@@ -0,0 +1,11 @@
+# test shape
+0 100
+0 0
+50 0
+50 50
+100 150
+100 200
+50 250
+50 300
+0 300
+0 250