diff --git a/t/stl.t b/t/stl.t
index 517e9e1f..3d443eda 100644
--- a/t/stl.t
+++ b/t/stl.t
@@ -18,19 +18,23 @@ my @points = ([3, 4], [8, 5], [1, 9]);  # XY coordinates of the facet vertices
 
 my $mesh = Slic3r::TriangleMesh->new(facets => [], vertices => []);
 
+# NOTE:
+# 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), [
-    [ $points[0], $points[1] ],
-    [ $points[1], $points[2] ],
-    [ $points[2], $points[0] ],
+    [ -1, $points[1] ],  # $points[0]
+    [ -1, $points[2] ],  # $points[1]
+    [ -1, $points[0] ],  # $points[2]
 ], 'horizontal';
 
-is_deeply lines(22, 20, 20), [ [ $points[1], $points[2] ] ], 'lower edge on layer';
-is_deeply lines(20, 20, 22), [ [ $points[0], $points[1] ] ], 'lower edge on layer';
-is_deeply lines(20, 22, 20), [ [ $points[2], $points[0] ] ], 'lower edge on layer';
+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]
+is_deeply lines(20, 22, 20), [ [ -1, $points[0] ] ], 'lower edge on layer';  # $points[2]
 
-is_deeply lines(20, 20, 10), [ [ $points[1], $points[0] ] ], 'upper edge on layer';
-is_deeply lines(10, 20, 20), [ [ $points[2], $points[1] ] ], 'upper edge on layer';
-is_deeply lines(20, 10, 20), [ [ $points[0], $points[2] ] ], 'upper edge on layer';
+is_deeply lines(20, 20, 10), [ [ -1, $points[0] ] ], 'upper edge on layer';  # $points[1]
+is_deeply lines(10, 20, 20), [ [ -1, $points[1] ] ], 'upper edge on layer';  # $points[2]
+is_deeply lines(20, 10, 20), [ [ -1, $points[2] ] ], 'upper edge on layer';  # $points[0]
 
 is_deeply lines(20, 15, 10), [                            ], 'upper vertex on layer';
 is_deeply lines(28, 20, 30), [                            ], 'lower vertex on layer';
@@ -39,7 +43,7 @@ is_deeply lines(28, 20, 30), [                            ], 'lower vertex on la
     my @z = (24, 10, 16);
     is_deeply lines(@z), [
         [
-            line_plane_intersection([ vertices(@z)->[0], vertices(@z)->[1] ]),
+            -1, # line_plane_intersection([ vertices(@z)->[0], vertices(@z)->[1] ]),
             line_plane_intersection([ vertices(@z)->[2], vertices(@z)->[0] ]),
         ]
     ], 'two edges intersect';
@@ -49,7 +53,7 @@ is_deeply lines(28, 20, 30), [                            ], 'lower vertex on la
     my @z = (16, 24, 10);
     is_deeply lines(@z), [
         [
-            line_plane_intersection([ vertices(@z)->[1], vertices(@z)->[2] ]),
+            -1, # line_plane_intersection([ vertices(@z)->[1], vertices(@z)->[2] ]),
             line_plane_intersection([ vertices(@z)->[0], vertices(@z)->[1] ]),
         ]
     ], 'two edges intersect';
@@ -59,7 +63,7 @@ is_deeply lines(28, 20, 30), [                            ], 'lower vertex on la
     my @z = (10, 16, 24);
     is_deeply lines(@z), [
         [
-            line_plane_intersection([ vertices(@z)->[2], vertices(@z)->[0] ]),
+            -1, # line_plane_intersection([ vertices(@z)->[2], vertices(@z)->[0] ]),
             line_plane_intersection([ vertices(@z)->[1], vertices(@z)->[2] ]),
         ]
     ], 'two edges intersect';
@@ -69,7 +73,7 @@ is_deeply lines(28, 20, 30), [                            ], 'lower vertex on la
     my @z = (24, 10, 20);
     is_deeply lines(@z), [
         [
-            line_plane_intersection([ vertices(@z)->[0], vertices(@z)->[1] ]),
+            -1, # line_plane_intersection([ vertices(@z)->[0], vertices(@z)->[1] ]),
             $points[2],
         ]
     ], 'one vertex on plane and one edge intersects';
@@ -79,7 +83,7 @@ is_deeply lines(28, 20, 30), [                            ], 'lower vertex on la
     my @z = (10, 20, 24);
     is_deeply lines(@z), [
         [
-            line_plane_intersection([ vertices(@z)->[2], vertices(@z)->[0] ]),
+            -1, # line_plane_intersection([ vertices(@z)->[2], vertices(@z)->[0] ]),
             $points[1],
         ]
     ], 'one vertex on plane and one edge intersects';
@@ -89,7 +93,7 @@ is_deeply lines(28, 20, 30), [                            ], 'lower vertex on la
     my @z = (20, 24, 10);
     is_deeply lines(@z), [
         [
-            line_plane_intersection([ vertices(@z)->[1], vertices(@z)->[2] ]),
+            -1, # line_plane_intersection([ vertices(@z)->[1], vertices(@z)->[2] ]),
             $points[0],
         ]
     ], 'one vertex on plane and one edge intersects';
@@ -97,8 +101,8 @@ is_deeply lines(28, 20, 30), [                            ], 'lower vertex on la
 
 my @lower = intersect(22, 20, 20);
 my @upper = intersect(20, 20, 10);
-is $lower[0]->facet_edge, 'bottom', 'bottom edge on layer';
-is $upper[0]->facet_edge, 'top', 'upper edge on layer';
+is $lower[0][Slic3r::TriangleMesh::I_FACET_EDGE], Slic3r::TriangleMesh::FE_BOTTOM, 'bottom edge on layer';
+is $upper[0][Slic3r::TriangleMesh::I_FACET_EDGE], Slic3r::TriangleMesh::FE_TOP, 'upper edge on layer';
 
 sub vertices {
     push @{$mesh->vertices}, map [ @{$points[$_]}, $_[$_] ], 0..2;
@@ -117,11 +121,11 @@ sub intersect {
 
 sub lines {
     my @lines = intersect(@_);
-    $_->a->[X] = sprintf('%.0f', $_->a->[X]) for @lines;
-    $_->a->[Y] = sprintf('%.0f', $_->a->[Y]) for @lines;
-    $_->b->[X] = sprintf('%.0f', $_->b->[X]) for @lines;
-    $_->b->[Y] = sprintf('%.0f', $_->b->[Y]) for @lines;
-    return [ map $_->points, @lines ];
+    #$_->a->[X] = sprintf('%.0f', $_->a->[X]) for @lines;
+    #$_->a->[Y] = sprintf('%.0f', $_->a->[Y]) for @lines;
+    $_->[Slic3r::TriangleMesh::I_B][X] = sprintf('%.0f', $_->[Slic3r::TriangleMesh::I_B][X]) for @lines;
+    $_->[Slic3r::TriangleMesh::I_B][Y] = sprintf('%.0f', $_->[Slic3r::TriangleMesh::I_B][Y]) for @lines;
+    return [ map [ -1, $_->[Slic3r::TriangleMesh::I_B] ], @lines ];
 }
 
 sub line_plane_intersection {