diff --git a/lib/Slic3r/GUI/3DScene.pm b/lib/Slic3r/GUI/3DScene.pm
index fcb54c018..9cd7cc1a3 100644
--- a/lib/Slic3r/GUI/3DScene.pm
+++ b/lib/Slic3r/GUI/3DScene.pm
@@ -19,7 +19,7 @@ package Slic3r::GUI::3DScene::Base;
 use strict;
 use warnings;
 
-use Wx qw(:timer);
+use Wx qw(:timer :bitmap);
 use Wx::Event qw(EVT_PAINT EVT_SIZE EVT_ERASE_BACKGROUND EVT_IDLE EVT_MOUSEWHEEL EVT_MOUSE_EVENTS EVT_TIMER);
 # must load OpenGL *before* Wx::GLCanvas
 use OpenGL qw(:glconstants :glfunctions :glufunctions :gluconstants);
@@ -173,7 +173,7 @@ sub new {
         my ($self, $event) = @_;
         return if ! $self->_layer_height_edited;
         return if $self->{layer_height_edit_last_object_id} == -1;
-        $self->_variable_layer_thickness_action(undef, 1);
+        $self->_variable_layer_thickness_action(undef);
     });
     
     return $self;
@@ -262,7 +262,7 @@ sub mouse_event {
             # A volume is selected and the mouse is hovering over a layer thickness bar.
             # Start editing the layer height.
             $self->_layer_height_edited(1);
-            $self->_variable_layer_thickness_action($e, 1);
+            $self->_variable_layer_thickness_action($e);
         } else {
             # Select volume in this 3D canvas.
             # Don't deselect a volume if layer editing is enabled. We want the object to stay selected
@@ -325,7 +325,7 @@ sub mouse_event {
         $self->Refresh;
     } elsif ($e->Dragging) {
         if ($self->_layer_height_edited && $object_idx_selected != -1) {
-            $self->_variable_layer_thickness_action($e, 0);
+            $self->_variable_layer_thickness_action($e);
         } elsif ($e->LeftIsDown) {
             # if dragging over blank area with left button, rotate
             if (defined $self->_drag_start_pos) {
@@ -1125,7 +1125,16 @@ sub draw_volumes {
         my $volume = $self->volumes->[$volume_idx];
 
         my $shader_active = 0;
-        if ($self->layer_editing_enabled && ! $fakecolor && $volume->selected && $self->{shader} && $volume->{layer_height_texture_data} && $volume->{layer_height_texture_cells}) {
+        if ($self->layer_editing_enabled && ! $fakecolor && $volume->selected && $self->{shader} && $volume->{layer_height_texture_data}) {
+            my $print_object = $self->{print}->get_object(int($volume->select_group_id / 1000000));
+            if (! defined($volume->{layer_height_texture_cells}) || $print_object->update_layer_height_profile) {
+                # Layer height profile was invalid before, now filled in with default data from layer height configuration
+                # and possibly from the layer height modifiers. Update the height texture.
+                $volume->{layer_height_texture_cells} = $print_object->generate_layer_height_texture(
+                    $volume->{layer_height_texture_data}->ptr,
+                    $self->{layer_preview_z_texture_height},
+                    $self->{layer_preview_z_texture_width});
+            }
             $self->{shader}->Enable;
             my $z_to_texture_row_id             = $self->{shader}->Map('z_to_texture_row');
             my $z_texture_row_to_normalized_id  = $self->{shader}->Map('z_texture_row_to_normalized');
@@ -1263,6 +1272,45 @@ sub draw_volumes {
     glDisableClientState(GL_VERTEX_ARRAY);
 }
 
+sub _variable_layer_thickness_load_overlay_image {
+    my ($self) = @_;
+
+    if (! $self->{layer_preview_annotation}->{loaded}) {
+        # Load a PNG with an alpha channel.
+        my $img = Wx::Image->new;
+        $img->LoadFile($Slic3r::var->("variable_layer_height_tooltip.png"), wxBITMAP_TYPE_PNG);
+        # Get RGB & alpha raw data from wxImage, interleave them into a Perl array.
+        my @rgb = unpack 'C*', $img->GetData();
+        my @alpha = unpack 'C*', $img->GetAlpha();
+        my $n_pixels = int(@alpha);
+        my @data = (0)x($n_pixels * 4);
+        for (my $i = 0; $i < $n_pixels; $i += 1) {
+            $data[$i*4  ] = $rgb[$i*3];
+            $data[$i*4+1] = $rgb[$i*3+1];
+            $data[$i*4+2] = $rgb[$i*3+2];
+            $data[$i*4+3] = $alpha[$i];
+        }
+        # Initialize a raw bitmap data.
+        my $params = $self->{layer_preview_annotation} = {
+            loaded => 1,
+            valid  => $n_pixels > 0,
+            width  => $img->GetWidth, 
+            height => $img->GetHeight,
+            data   => OpenGL::Array->new_list(GL_UNSIGNED_BYTE, @data),
+            texture_id => glGenTextures_p(1)
+        };
+        # Create and initialize a texture with the raw data.
+        glBindTexture(GL_TEXTURE_2D, $params->{texture_id});
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 1);
+        glTexImage2D_c(GL_TEXTURE_2D, 0, GL_RGBA8, $params->{width}, $params->{height}, 0, GL_RGBA, GL_UNSIGNED_BYTE, $params->{data}->ptr);
+        glBindTexture(GL_TEXTURE_2D, 0);
+    }
+
+    return $self->{layer_preview_annotation}->{valid};
+}
+
 sub draw_active_object_annotations {
     # $fakecolor is a boolean indicating, that the objects shall be rendered in a color coding the object index for picking.
     my ($self) = @_;
@@ -1324,6 +1372,28 @@ sub draw_active_object_annotations {
     glBindTexture(GL_TEXTURE_2D, 0);
     $self->{shader}->Disable;
 
+    # Paint the tooltip.
+    if ($self->_variable_layer_thickness_load_overlay_image) {
+        glColor4f(1.,1.,1.,1.);
+        glDisable(GL_LIGHTING);
+        glEnable(GL_BLEND);
+        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+        glEnable(GL_TEXTURE_2D);
+        glBindTexture(GL_TEXTURE_2D, $self->{layer_preview_annotation}->{texture_id});
+        glBegin(GL_QUADS);
+        my $gap = 10/$self->_zoom;
+        my ($l, $r, $t, $b) = ($bar_left - $self->{layer_preview_annotation}->{width}/$self->_zoom - $gap, $bar_left - $gap, $bar_bottom + $self->{layer_preview_annotation}->{height}/$self->_zoom + $gap, $bar_bottom + $gap);
+        glTexCoord2d(0.,1.); glVertex3f($l, $b, 0);
+        glTexCoord2d(1.,1.); glVertex3f($r, $b, 0);
+        glTexCoord2d(1.,0.); glVertex3f($r, $t, 0);
+        glTexCoord2d(0.,0.); glVertex3f($l, $t, 0);
+        glEnd();
+        glBindTexture(GL_TEXTURE_2D, 0);
+        glDisable(GL_TEXTURE_2D);
+        glDisable(GL_BLEND);
+        glEnable(GL_LIGHTING);
+    }
+
     # Paint the graph.
     my $object_idx = int($volume->select_group_id / 1000000);
     my $print_object = $self->{print}->get_object($object_idx);
@@ -1593,11 +1663,6 @@ sub load_object {
     if ($print && $obj_idx < $print->object_count) {
         # Generate the layer height texture. Allocate data for the 0th and 1st mipmap levels.
         $layer_height_texture_data = OpenGL::Array->new($self->{layer_preview_z_texture_width}*$self->{layer_preview_z_texture_height}*5, GL_UNSIGNED_BYTE);
-#        $print->get_object($obj_idx)->update_layer_height_profile_from_ranges();
-        $layer_height_texture_cells = $print->get_object($obj_idx)->generate_layer_height_texture(
-            $layer_height_texture_data->ptr,
-            $self->{layer_preview_z_texture_height},
-            $self->{layer_preview_z_texture_width});
     }
     
     my @volumes_idx = ();
diff --git a/var/variable_layer_height_tooltip.png b/var/variable_layer_height_tooltip.png
new file mode 100644
index 000000000..182005292
Binary files /dev/null and b/var/variable_layer_height_tooltip.png differ
diff --git a/xs/src/libslic3r/Model.hpp b/xs/src/libslic3r/Model.hpp
index 963bd7c85..e6e98bc01 100644
--- a/xs/src/libslic3r/Model.hpp
+++ b/xs/src/libslic3r/Model.hpp
@@ -114,6 +114,9 @@ public:
     DynamicPrintConfig config;
     // Variation of a layer thickness for spans of Z coordinates.
     t_layer_height_ranges layer_height_ranges;
+    // Profile of increasing z to a layer height, to be linearly interpolated when calculating the layers.
+    // The pairs of <z, layer_height> are packed into a 1D array to simplify handling by the Perl XS.
+    std::vector<coordf_t> layer_height_profile;
 
     /* This vector accumulates the total translation applied to the object by the
         center_around_origin() method. Callers might want to apply the same translation
diff --git a/xs/src/libslic3r/Print.cpp b/xs/src/libslic3r/Print.cpp
index 6e2fdb4f3..539562a16 100644
--- a/xs/src/libslic3r/Print.cpp
+++ b/xs/src/libslic3r/Print.cpp
@@ -8,43 +8,6 @@
 
 namespace Slic3r {
 
-template <class StepClass>
-bool
-PrintState<StepClass>::is_started(StepClass step) const
-{
-    return this->started.find(step) != this->started.end();
-}
-
-template <class StepClass>
-bool
-PrintState<StepClass>::is_done(StepClass step) const
-{
-    return this->done.find(step) != this->done.end();
-}
-
-template <class StepClass>
-void
-PrintState<StepClass>::set_started(StepClass step)
-{
-    this->started.insert(step);
-}
-
-template <class StepClass>
-void
-PrintState<StepClass>::set_done(StepClass step)
-{
-    this->done.insert(step);
-}
-
-template <class StepClass>
-bool
-PrintState<StepClass>::invalidate(StepClass step)
-{
-    bool invalidated = this->started.erase(step) > 0;
-    this->done.erase(step);
-    return invalidated;
-}
-
 template class PrintState<PrintStep>;
 template class PrintState<PrintObjectStep>;
 
diff --git a/xs/src/libslic3r/Print.hpp b/xs/src/libslic3r/Print.hpp
index a0392290d..99582d65d 100644
--- a/xs/src/libslic3r/Print.hpp
+++ b/xs/src/libslic3r/Print.hpp
@@ -33,14 +33,18 @@ enum PrintObjectStep {
 template <class StepType>
 class PrintState
 {
-    public:
+public:
     std::set<StepType> started, done;
     
-    bool is_started(StepType step) const;
-    bool is_done(StepType step) const;
-    void set_started(StepType step);
-    void set_done(StepType step);
-    bool invalidate(StepType step);
+    bool is_started(StepType step) const { return this->started.find(step) != this->started.end(); }
+    bool is_done(StepType step) const { return this->done.find(step) != this->done.end(); }
+    void set_started(StepType step) { this->started.insert(step); }
+    void set_done(StepType step) { this->done.insert(step); }
+    bool invalidate(StepType step) {
+        bool invalidated = this->started.erase(step) > 0;
+        this->done.erase(step);
+        return invalidated;
+    }
 };
 
 // A PrintRegion object represents a group of volumes to print
@@ -143,7 +147,7 @@ public:
 
     // Process layer_height_ranges, the raft layers and first layer thickness into layer_height_profile.
     // The layer_height_profile may be later modified interactively by the user to refine layers at sloping surfaces.
-    void update_layer_height_profile();
+    bool update_layer_height_profile();
 
     // Collect the slicing parameters, to be used by variable layer thickness algorithm,
     // by the interactive layer height editor and by the printing process itself.
diff --git a/xs/src/libslic3r/PrintObject.cpp b/xs/src/libslic3r/PrintObject.cpp
index 94001cb38..8091db973 100644
--- a/xs/src/libslic3r/PrintObject.cpp
+++ b/xs/src/libslic3r/PrintObject.cpp
@@ -49,6 +49,7 @@ PrintObject::PrintObject(Print* print, ModelObject* model_object, const Bounding
     
     this->reload_model_instances();
     this->layer_height_ranges = model_object->layer_height_ranges;
+    this->layer_height_profile = model_object->layer_height_profile;
 }
 
 bool
@@ -949,8 +950,9 @@ SlicingParameters PrintObject::slicing_parameters() const
         unscale(this->size.z), this->print()->object_extruders());
 }
 
-void PrintObject::update_layer_height_profile()
+bool PrintObject::update_layer_height_profile()
 {
+    bool updated = false;
     if (this->layer_height_profile.empty()) {
         if (0)
 //        if (this->layer_height_profile.empty())
@@ -958,7 +960,9 @@ void PrintObject::update_layer_height_profile()
                 this->model_object()->volumes);
         else
             this->layer_height_profile = layer_height_profile_from_ranges(this->slicing_parameters(), this->layer_height_ranges);
+        updated = true;
     }
+    return updated;
 }
 
 // 1) Decides Z positions of the layers,
diff --git a/xs/xsp/Model.xsp b/xs/xsp/Model.xsp
index aedc1f7dc..1859779b9 100644
--- a/xs/xsp/Model.xsp
+++ b/xs/xsp/Model.xsp
@@ -4,6 +4,7 @@
 #include <xsinit.h>
 #include "libslic3r/Model.hpp"
 #include "libslic3r/PrintConfig.hpp"
+#include "libslic3r/Slicing.hpp"
 %}
 
 %name{Slic3r::Model} class Model {
@@ -169,6 +170,7 @@ ModelMaterial::attributes()
     void set_layer_height_ranges(t_layer_height_ranges ranges)
         %code%{ THIS->layer_height_ranges = ranges; %};
 
+
     Ref<Pointf3> origin_translation()
         %code%{ RETVAL = &THIS->origin_translation; %};
     void set_origin_translation(Pointf3* point)
diff --git a/xs/xsp/Print.xsp b/xs/xsp/Print.xsp
index d2fca6105..f7a3fa118 100644
--- a/xs/xsp/Print.xsp
+++ b/xs/xsp/Print.xsp
@@ -3,7 +3,6 @@
 %{
 #include <xsinit.h>
 #include "libslic3r/Print.hpp"
-#include "libslic3r/Slicing.hpp"
 #include "libslic3r/PlaceholderParser.hpp"
 %}
 
@@ -121,6 +120,8 @@ _constant()
     void _infill();
     void _generate_support_material();
 
+    bool update_layer_height_profile();
+
     void adjust_layer_height_profile(coordf_t z, coordf_t layer_thickness_delta, coordf_t band_width, int action)
         %code%{ 
             THIS->update_layer_height_profile();