From db266cde9f6d85b3e8f4e12d91211fc3840086da Mon Sep 17 00:00:00 2001
From: Alessandro Ranellucci <aar@cpan.org>
Date: Sat, 22 Jun 2013 20:32:39 +0200
Subject: [PATCH] Little optimizations in slicing

---
 lib/Slic3r/TriangleMesh.pm | 10 +++++-----
 t/slice.t                  | 14 ++++++++------
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/lib/Slic3r/TriangleMesh.pm b/lib/Slic3r/TriangleMesh.pm
index 6e9054716..755816b6a 100644
--- a/lib/Slic3r/TriangleMesh.pm
+++ b/lib/Slic3r/TriangleMesh.pm
@@ -459,10 +459,9 @@ sub intersect_facet {
     my @edge_ids            = @{$self->facets_edges->[$facet_id]};
     my @edge_vertices_ids   = $self->_facet_edges($facet_id);
     
-    my (@lines, @points, @intersection_points, @points_on_layer) = ();
+    my (@points, @intersection_points, @points_on_layer) = ();
         
     for my $e (0..2) {
-        my $edge_id         = $edge_ids[$e];
         my ($a_id, $b_id)   = @{$edge_vertices_ids[$e]};
         my ($a, $b)         = @vertices{$a_id, $b_id};
         #printf "Az = %f, Bz = %f, z = %f\n", $a->[Z], $b->[Z], $z;
@@ -474,7 +473,9 @@ sub intersect_facet {
                 ($a, $b) = ($b, $a);
                 ($a_id, $b_id) = ($b_id, $a_id);
             }
-            push @lines, pack I_FMT, (
+            # We assume that this method is never being called for horizontal
+            # facets, so no other edge is going to be on this layer.
+            return pack I_FMT, (
                 $b->[X], $b->[Y],       # I_B
                 $a_id,                  # I_A_ID
                 $b_id,                  # I_B_ID
@@ -504,14 +505,13 @@ sub intersect_facet {
                 $b->[X] + ($a->[X] - $b->[X]) * ($z - $b->[Z]) / ($a->[Z] - $b->[Z]),
                 $b->[Y] + ($a->[Y] - $b->[Y]) * ($z - $b->[Z]) / ($a->[Z] - $b->[Z]),
                 undef,
-                $edge_id,
+                $edge_ids[$e],
             ];
             push @intersection_points, $#points;
             #print "Intersects at $z!\n";
         }
     }
     
-    return @lines if @lines;
     if (@points_on_layer == 2 && @intersection_points == 1) {
         $points[ $points_on_layer[1] ] = undef;
         @points = grep $_, @points;
diff --git a/t/slice.t b/t/slice.t
index e47929f0f..8032924fb 100644
--- a/t/slice.t
+++ b/t/slice.t
@@ -2,7 +2,7 @@ use Test::More;
 use strict;
 use warnings;
 
-plan tests => 17;
+plan tests => 16;
 
 BEGIN {
     use FindBin;
@@ -20,11 +20,13 @@ my @points = ([3, 4], [8, 5], [1, 9]);  # XY coordinates of the facet vertices
 # the first point of the intersection lines is replaced by -1 because TriangleMesh.pm
 # is saving memory and doesn't store point A anymore since it's not actually needed.
 
-is_deeply lines(20, 20, 20), [
-    [ -1, $points[1] ],  # $points[0]
-    [ -1, $points[2] ],  # $points[1]
-    [ -1, $points[0] ],  # $points[2]
-], 'horizontal';
+# We disable this test because intersect_facet() now assumes we never feed a horizontal
+# facet to it.
+# is_deeply lines(20, 20, 20), [
+#     [ -1, $points[1] ],  # $points[0]
+#     [ -1, $points[2] ],  # $points[1]
+#     [ -1, $points[0] ],  # $points[2]
+# ], 'horizontal';
 
 is_deeply lines(22, 20, 20), [ [ -1, $points[2] ] ], 'lower edge on layer';  # $points[1]
 is_deeply lines(20, 20, 22), [ [ -1, $points[1] ] ], 'lower edge on layer';  # $points[0]