diff --git a/solidify/face.c b/solidify/face.c
index 18f8d8a..d444a14 100644
--- a/solidify/face.c
+++ b/solidify/face.c
@@ -26,15 +26,20 @@
 
 
 #define	CACHE_DIR	".cache"
+#define	DEFAULT_STEP	1		/* 1 mm */
+#define	MIN_STEP	0.005		/* 5 um */
 
 
-static struct face *read_file(const char *name)
+struct coord {
+	float x, y, z;
+};
+
+
+static struct coord *load_file(const char *name)
 {
 	FILE *file;
-	struct face *f;
-	struct histo *h;
-	float x, y, z;
-	int xi, yi, zi;
+	struct coord *v, *n;
+	int s;
 
 	if (!strcmp(name, "-")) {
 		file = stdin;
@@ -59,19 +64,76 @@ static struct face *read_file(const char *name)
 			}
 		}
 	}
-	f = alloc_type(struct face);
-	f->a = new_array();
 
-	while (fscanf(file, "%f,%f,%f\r\n", &x, &y, &z) == 3) {
-		/* @@@ hack - should auto-scale */
-		xi = round(x*10.0);
-		yi = round(y*10.0);
-		zi = round(z*40.0);
-		set(f->a, xi, yi, zi);
+	v = n = alloc_type(struct coord);
+	s = 1;
+
+	while (fscanf(file, "%f,%f,%f\r\n", &n->x, &n->y, &n->z) == 3) {
+		n++;
+		if (n-v == s) {
+			struct coord *tmp;
+
+			s += s;
+			tmp = realloc(v, sizeof(struct coord)*s);
+			if (!tmp) {
+				perror("realloc");
+				exit(1);
+			}
+			n = n-v+tmp;
+			v = tmp;
+		}
 	}
 	if (file != stdin)
 		(void) fclose(file);
 
+	n->x = n->y = n->z = 0;
+	return v;
+}
+
+
+static void adjust_step(double *step, double delta)
+{
+	double n = round(delta/MIN_STEP);
+	double s = n*MIN_STEP;
+
+	if (n && s < *step)
+		*step = s;
+}
+
+
+static struct face *read_file(const char *name)
+{
+	struct coord *v, *p;
+	struct face *f;
+	struct histo *h;
+	int xi, yi, zi;
+
+	v = load_file(name);
+
+	f = alloc_type(struct face);
+	f->a = new_array();
+
+	/*
+	 * Hack: the MDX-15 measures bumps along the x axis with 25 um
+	 * resolution, so we just ignore the x resultion we find and use the
+	 * y resolution instead.
+	 */
+	f->x_step = f->y_step =f->z_step = DEFAULT_STEP;
+	for (p = v; p[1].x || p[1].y || p[1].z; p++) {
+		adjust_step(&f->y_step, fabs(p[0].y-p[1].y));
+		adjust_step(&f->z_step, fabs(p[0].z-p[1].z));
+	}
+	f->x_step = f->y_step;
+
+	for (p = v; p->x || p->y || p->z; p++) {
+		xi = round(p->x/f->x_step);
+		yi = round(p->y/f->y_step);
+		zi = round(p->z/f->z_step);
+		set(f->a, xi, yi, zi);
+	}
+
+	free(v);
+
 	f->sx = f->a->max_x-f->a->min_x+1;
 	f->sy = f->a->max_y-f->a->min_y+1;
 
@@ -87,6 +149,7 @@ static struct face *read_file(const char *name)
 	f->m.a[0][1] = f->m.a[1][0] = 0;
 	f->m.b[0] = f->m.b[1] = 0;
 
+	fprintf(stderr, "%g %g %g\n", f->x_step, f->y_step, f->z_step);
 	fprintf(stderr, "%d-%d / %d-%d / %d-%d\n",
 	    f->a->min_x, f->a->max_x, f->a->min_y, f->a->max_y,
 	    f->a->min_z, f->a->max_z);
diff --git a/solidify/face.h b/solidify/face.h
index d524604..46fba86 100644
--- a/solidify/face.h
+++ b/solidify/face.h
@@ -19,6 +19,7 @@
 
 struct face {
 	struct array *a;
+	double x_step, y_step, z_step;
 	int sx, sy;	/* size */
 	int cx, cy;	/* center */
 	int z_ref;
diff --git a/solidify/solidify.c b/solidify/solidify.c
index f7c742e..871abd1 100644
--- a/solidify/solidify.c
+++ b/solidify/solidify.c
@@ -127,17 +127,27 @@ static void usage(const char *name)
 int main(int argc, char **argv)
 {
 	gtk_init(&argc, &argv);
+	setlocale(LC_ALL, "C"); /* damage control */
+
 	switch (argc) {
 	case 4:
 		break;
 	default:
 		usage(*argv);
 	}
-	setlocale(LC_ALL, "C"); /* damage control */
+
 	solid.a = read_face(argv[1]);
 	solid.b = read_face(argv[2]);
-	solid.dist = atof(argv[3])/0.025; /* @@@ hack */
+	if (solid.a->x_step != solid.a->x_step ||
+	    solid.a->y_step != solid.a->y_step ||
+	    solid.a->z_step != solid.a->z_step) {
+		fprintf(stderr, "both faces must have the same resolution\n");
+		exit(1);
+	}
+	solid.dist = atof(argv[3])/solid.a->z_step;
+
 	gui();
+
 	if (!isatty(1))
 		povray(&solid);