From 005dcc308ce0219a4acc607807f1d361746b7435 Mon Sep 17 00:00:00 2001
From: Werner Almesberger <werner@almesberger.net>
Date: Thu, 15 Jan 2015 02:00:05 -0300
Subject: [PATCH] slicer/slicer.c: rewrite - we now consider all non-horizontal
 facets

---
 slicer/slice.c | 134 ++++++++++++++++++++++---------------------------
 1 file changed, 59 insertions(+), 75 deletions(-)

diff --git a/slicer/slice.c b/slicer/slice.c
index cb6ddff..cf4c04e 100644
--- a/slicer/slice.c
+++ b/slicer/slice.c
@@ -20,22 +20,19 @@
 #include "slice.h"
 
 
-struct line {
-	float ax, ay;
-	float bx, by;
-	float cz;
-	struct line *next;
+struct facet {
+	struct v a, b, c;
+	struct facet *next;
 };
 
 
 struct z {
 	float z;
-	bool present;
-	struct line *lines;
 };
 
 
 static GTree *tree;
+static struct facet *facets = NULL;
 
 
 /* ----- Bounding box ------------------------------------------------------ */
@@ -73,44 +70,23 @@ static inline bool eq(float a, float b)
 }
 
 
-static struct z *get_z(float z)
-{
-	struct z *base;
-
-	base = g_tree_lookup(tree, &z);
-	if (base)
-		return base;
-	base = alloc_type(struct z);
-	base->z = z;
-	base->present = 0;
-	base->lines = NULL;
-	g_tree_insert(tree, &base->z, base);
-	return base;
-}
-
-
 static void mark_z(float z)
 {
-	struct z *base;
+	struct z *e;
 
-	base = get_z(z);
-	base->present = 1;
+	e = g_tree_lookup(tree, &z);
+	if (e)
+		return;
+	e = alloc_type(struct z);
+	e->z = z;
+	g_tree_insert(tree, &e->z, e);
 }
 
 
 static void add(const struct v *a, const struct v *b, const struct v *c)
 {
 	float cross;
-	struct z *z;
-	struct line *line;
-
-	if (eq(a->x, b->x) && eq(a->y, b->y)) {
-fprintf(stderr, "zero point\n");
-		return;
-	}
-
-	if (c->z < a->z)
-		return;
+	struct facet *f;
 
 	cross = (b->x - a->x) * (c->y - a->y) - (b->y - a->y) * (c->x - a->x);
 	if (!eq(cross, 0)) {
@@ -122,16 +98,14 @@ fprintf(stderr, "zero point\n");
 
 	bbox(a->x, a->y);
 	bbox(b->x, b->y);
+	bbox(c->x, c->y);
 
-	z = get_z(a->z);
-	line = alloc_type(struct line);
-	line->ax = a->x;
-	line->ay = a->y;
-	line->bx = b->x;
-	line->by = b->y;
-	line->cz = c->z;
-	line->next = z->lines;
-	z->lines = line;
+	f = alloc_type(struct facet);
+	f->a = *a;
+	f->b = *b;
+	f->c = *c;
+	f->next = facets;
+	facets = f;
 }
 
 
@@ -139,16 +113,12 @@ void slice(struct v f[3])
 {
 	bool ab = eq(f[0].z, f[1].z);
 	bool bc = eq(f[1].z, f[2].z);
-	bool ac = eq(f[0].z, f[2].z);
 
-	if (ab && bc)
+	if (ab && bc) {
 		mark_z(f[0].z);
-	else if (ab)
-		add(f + 0, f + 1, f + 2);
-	else if (bc)
-		add(f + 1, f + 2, f + 0);
-	else if (ac)
-		add(f + 0, f + 2, f + 1);
+		return;
+	}
+	add(f + 0, f + 1, f + 2);
 }
 
 
@@ -170,9 +140,6 @@ static gboolean check_z(gpointer key, gpointer value, gpointer data)
 	float d;
 	int n, i;
 
-	if (!z->present)
-		return 0;
-
 	if (ctx->first) {
 		ctx->first = 0;
 		ctx->z0 = z->z;
@@ -212,31 +179,51 @@ void slice_intermediate(float z_step)
 /* ----- Dumping ----------------------------------------------------------- */
 
 
-static gboolean dump_layer(gpointer key, gpointer value, gpointer data)
+static bool cut(const struct v *a, const struct v *b, float z, struct v *res)
 {
-	const struct z *z0 = data;
-	const struct z *z1 = value;
-	const struct line *line;
+	float dx, dy, dz;
+	float f;
 
-	if (z0->z > z1->z)
+	if (a->z > b->z)
+		return cut(b, a, z, res);
+	if (eq(a->z, b->z))
 		return 0;
-	if (!z1->present)
+	if (a->z > z || b->z < z || eq(b->z, z))
 		return 0;
-	for (line = z0->lines; line; line = line->next)
-		if (line->cz > z1->z)
-			printf("%f %f %f\n%f %f %f\n\n\n",
-			    line->ax, line->ay, z1->z,
-			    line->bx, line->by, z1->z);
-	return 0;
+
+	dx = b->x - a->x;
+	dy = b->y - a->y;
+	dz = b->z - a->z;
+
+	f = (z - a->z) / dz;
+
+	res->x = f * dx + a->x;
+	res->y = f * dy + a->y;
+	res->z = z;
+
+	return 1;
 }
 
 
-static gboolean dump_range(gpointer key, gpointer value, gpointer data)
+static gboolean dump_layer(gpointer key, gpointer value, gpointer data)
 {
 	const struct z *z = value;
+	const struct facet *f;
+	struct v p1, p2;
 
-	if (z->present)
-		g_tree_foreach(tree, dump_layer, value);
+	for (f = facets; f; f = f->next) {
+		if (cut(&f->a, &f->b, z->z, &p1)) {
+			if (!cut(&f->a, &f->c, z->z, &p2) &&
+			    !cut(&f->b, &f->c, z->z, &p2))
+				continue;
+		} else if (!cut(&f->a, &f->c, z->z, &p1) ||
+		    !cut(&f->b, &f->c, z->z, &p2)) {
+			continue;
+		}
+		printf("%f %f %f\n%f %f %f\n\n\n",
+		    p1.x, p1.y, z->z, p2.x, p2.y, z->z);
+
+	}
 	return 0;
 }
 
@@ -246,9 +233,6 @@ static gboolean dump_box(gpointer key, gpointer value, gpointer data)
 	const struct z *z = value;
 	float box = *(float *) data;
 
-	if (!z->present)
-		return 0;
-
 	printf("%f %f %f\n%f %f %f\n%f %f %f\n%f %f %f\n%f %f %f\n\n\n",
 	    min_x - box, min_y - box, z->z,
 	    max_x + box, min_y - box, z->z,
@@ -262,7 +246,7 @@ static gboolean dump_box(gpointer key, gpointer value, gpointer data)
 
 void slice_dump(float box)
 {
-	g_tree_foreach(tree, dump_range, NULL);
+	g_tree_foreach(tree, dump_layer, NULL);
 	if (box && !first)
 		g_tree_foreach(tree, dump_box, &box);
 }