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ENH: improve the support of blade-shape overhangs
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1. reduce the gap between blade-shape overhang and support
   github: SoftFever#3667
2. improve sharp tail detection of blade-shape overhangs by introducing
   lslices_extrudable.
   github: SoftFever#2786, SoftFever#3367
   jira: STUDIO-5065, STUDIO-6038

Change-Id: I4e899eace1aa28b100a6f4ce2b8d740c317f5530
(cherry picked from commit 08328b848e39c345b6c7b64021d1e0f04df24d08)
(cherry picked from commit 22056d5f7e7bef5574b53fc0453781cd365bf0e1)
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@ArthurBambulab @Noisyfox
ArthurBambulab authored and Noisyfox committed Jan 27, 2025
1 parent 17cdce9 commit c185e08
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Showing 3 changed files with 37 additions and 38 deletions.
3 changes: 2 additions & 1 deletion src/libslic3r/Layer.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -139,7 +139,7 @@ class Layer
// BBS
mutable ExPolygons sharp_tails;
mutable ExPolygons cantilevers;
mutable std::map<const ExPolygon*, float> sharp_tails_height;
mutable std::vector<float> sharp_tails_height;

// Collection of expolygons generated by slicing the possibly multiple meshes of the source geometry
// (with possibly differing extruder ID and slicing parameters) and merged.
Expand All @@ -150,6 +150,7 @@ class Layer
// These lslices are also used to detect overhangs and overlaps between successive layers, therefore it is important
// that the 1st lslice is not compensated by the Elephant foot compensation algorithm.
ExPolygons lslices;
ExPolygons lslices_extrudable; // BBS: the extrudable part of lslices used for tree support
std::vector<BoundingBox> lslices_bboxes;

// BBS
Expand Down
16 changes: 8 additions & 8 deletions src/libslic3r/Support/SupportMaterial.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1412,6 +1412,7 @@ static inline ExPolygons detect_overhangs(
const coordf_t max_bridge_length = scale_(object_config.max_bridge_length.value);
const bool bridge_no_support = object_config.bridge_no_support.value;
const coordf_t xy_expansion = scale_(object_config.support_expansion.value);
float lower_layer_offset = 0;

if (layer_id == 0)
{
Expand All @@ -1424,7 +1425,7 @@ static inline ExPolygons detect_overhangs(
!(bbox_size.x() > length_thresh_well_supported && bbox_size.y() > length_thresh_well_supported))
{
layer.sharp_tails.push_back(slice);
layer.sharp_tails_height.insert({ &slice, layer.height });
layer.sharp_tails_height.push_back(layer.height);
}
}
}
Expand All @@ -1444,7 +1445,6 @@ static inline ExPolygons detect_overhangs(
}
}

float lower_layer_offset = 0;
for (LayerRegion *layerm : layer.regions()) {
// Extrusion width accounts for the roundings of the extrudates.
// It is the maximum widh of the extrudate.
Expand Down Expand Up @@ -1506,7 +1506,7 @@ static inline ExPolygons detect_overhangs(
if (is_sharp_tail) {
ExPolygons overhang = diff_ex({ expoly }, lower_layer_expolys);
layer.sharp_tails.push_back(expoly);
layer.sharp_tails_height.insert({ &expoly, accum_height });
layer.sharp_tails_height.push_back(accum_height);
overhang = offset_ex(overhang, 0.05 * fw);
polygons_append(diff_polygons, to_polygons(overhang));
}
Expand Down Expand Up @@ -1546,7 +1546,7 @@ static inline ExPolygons detect_overhangs(
if (layer.lower_layer) {
for (ExPolygon& poly : overhang_areas) {
float fw = float(layer.regions().front()->flow(frExternalPerimeter).scaled_width());
auto cluster_boundary_ex = intersection_ex(poly, offset_ex(layer.lower_layer->lslices, scale_(0.5)));
auto cluster_boundary_ex = intersection_ex(poly, offset_ex(layer.lower_layer->lslices, std::max(fw, lower_layer_offset) + scale_(0.1)));
Polygons cluster_boundary = to_polygons(cluster_boundary_ex);
if (cluster_boundary.empty()) continue;
double dist_max = 0;
Expand Down Expand Up @@ -2216,9 +2216,9 @@ SupportGeneratorLayersPtr PrintObjectSupportMaterial::top_contact_layers(
}

// 2.3 check whether sharp tail exceed the max height
for (const auto& lower_sharp_tail_height : lower_layer_sharptails_height) {
if (lower_sharp_tail_height.first->overlaps(expoly)) {
accum_height += lower_sharp_tail_height.second;
for (size_t i = 0; i < lower_layer_sharptails_height.size();i++) {
if (lower_layer_sharptails[i].overlaps(expoly)) {
accum_height += lower_layer_sharptails_height[i];
break;
}
}
Expand All @@ -2243,7 +2243,7 @@ SupportGeneratorLayersPtr PrintObjectSupportMaterial::top_contact_layers(
if (is_sharp_tail) {
ExPolygons overhang = diff_ex({ expoly }, lower_layer->lslices);
layer->sharp_tails.push_back(expoly);
layer->sharp_tails_height.insert({ &expoly, accum_height });
layer->sharp_tails_height.push_back( accum_height );
append(overhangs_per_layers[layer_nr], overhang);
#ifdef SUPPORT_TREE_DEBUG_TO_SVG
SVG svg(get_svg_filename(std::to_string(layer->print_z), "sharp_tail"), object.bounding_box());
Expand Down
56 changes: 27 additions & 29 deletions src/libslic3r/Support/TreeSupport.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -752,6 +752,17 @@ void TreeSupport::detect_overhangs(bool check_support_necessity/* = false*/)
max_cantilever_dist = 0;
m_highest_overhang_layer = 0;

// calc the extrudable expolygons of each layer
tbb::parallel_for(tbb::blocked_range<size_t>(0, m_object->layer_count()),
[&](const tbb::blocked_range<size_t>& range) {
for (size_t layer_nr = range.begin(); layer_nr < range.end(); layer_nr++) {
if (m_object->print()->canceled())
break;
Layer* layer = m_object->get_layer(layer_nr);
// Filter out areas whose diameter that is smaller than extrusion_width, but we don't want to lose any details.
layer->lslices_extrudable = intersection_ex(layer->lslices, offset2_ex(layer->lslices, -extrusion_width_scaled / 2, extrusion_width_scaled));
}
});
// main part of overhang detection can be parallel
tbb::parallel_for(tbb::blocked_range<size_t>(0, m_object->layer_count()),
[&](const tbb::blocked_range<size_t>& range) {
Expand All @@ -770,7 +781,7 @@ void TreeSupport::detect_overhangs(bool check_support_necessity/* = false*/)
if (!((bbox_size.x() > length_thresh_well_supported && bbox_size.y() > length_thresh_well_supported))
&& g_config_support_sharp_tails) {
layer->sharp_tails.push_back(slice);
layer->sharp_tails_height.insert({ &slice, layer->height });
layer->sharp_tails_height.push_back(layer->height);
}
}
continue;
Expand All @@ -780,21 +791,8 @@ void TreeSupport::detect_overhangs(bool check_support_necessity/* = false*/)
coordf_t lower_layer_offset = layer_nr < enforce_support_layers ? -0.15 * extrusion_width : (float)lower_layer->height / tan(threshold_rad);
//lower_layer_offset = std::min(lower_layer_offset, extrusion_width);
coordf_t support_offset_scaled = scale_(lower_layer_offset);
// Filter out areas whose diameter that is smaller than extrusion_width. Do not use offset2() for this purpose!
ExPolygons lower_polys;
for (const ExPolygon& expoly : lower_layer->lslices) {
if (!offset_ex(expoly, -extrusion_width_scaled / 2).empty()) {
lower_polys.emplace_back(expoly);
}
}
ExPolygons curr_polys;
std::vector<const ExPolygon*> curr_poly_ptrs;
for (const ExPolygon& expoly : layer->lslices) {
if (!offset_ex(expoly, -extrusion_width_scaled / 2).empty()) {
curr_polys.emplace_back(expoly);
curr_poly_ptrs.emplace_back(&expoly);
}
}
ExPolygons& curr_polys = layer->lslices_extrudable;
ExPolygons& lower_polys = lower_layer->lslices_extrudable;

// normal overhang
ExPolygons lower_layer_offseted = offset_ex(lower_polys, support_offset_scaled, SUPPORT_SURFACES_OFFSET_PARAMETERS);
Expand All @@ -803,24 +801,24 @@ void TreeSupport::detect_overhangs(bool check_support_necessity/* = false*/)
if (is_auto(stype) && g_config_support_sharp_tails)
{
// BBS detect sharp tail
for (const ExPolygon* expoly : curr_poly_ptrs) {
for (const ExPolygon& expoly : curr_polys) {
bool is_sharp_tail = false;
// 1. nothing below
// this is a sharp tail region if it's floating and non-ignorable
if (!overlaps(offset_ex(*expoly, 0.5 * extrusion_width_scaled), lower_polys)) {
is_sharp_tail = !offset_ex(*expoly, -0.1 * extrusion_width_scaled).empty();
if (!overlaps(offset_ex(expoly, 0.5 * extrusion_width_scaled), lower_polys)) {
is_sharp_tail = !offset_ex(expoly, -0.1 * extrusion_width_scaled).empty();
}

if (is_sharp_tail) {
ExPolygons overhang = diff_ex({ *expoly }, lower_polys);
layer->sharp_tails.push_back(*expoly);
layer->sharp_tails_height.insert({ expoly, layer->height });
ExPolygons overhang = diff_ex({ expoly }, lower_polys);
layer->sharp_tails.push_back(expoly);
layer->sharp_tails_height.push_back(layer->height);
append(overhang_areas, overhang);

if (!overhang.empty()) {
has_sharp_tails = true;
#ifdef SUPPORT_TREE_DEBUG_TO_SVG
SVG::export_expolygons(debug_out_path("sharp_tail_orig_%.02f.svg", layer->print_z), { expoly });
SVG::export_expolygons(debug_out_path("sharp_tail_orig_%.02f.svg", layer->print_z), { expoly });
#endif
}
}
Expand All @@ -834,7 +832,7 @@ void TreeSupport::detect_overhangs(bool check_support_necessity/* = false*/)
// check cantilever
{
// lower_layer_offset may be very small, so we need to do max and then add 0.1
auto cluster_boundary_ex = intersection_ex(poly, offset_ex(lower_layer->lslices, scale_(std::max(extrusion_width,lower_layer_offset)+0.1)));
auto cluster_boundary_ex = intersection_ex(poly, offset_ex(lower_polys, scale_(std::max(extrusion_width,lower_layer_offset)+0.1)));
Polygons cluster_boundary = to_polygons(cluster_boundary_ex);
if (cluster_boundary.empty()) continue;
double dist_max = 0;
Expand Down Expand Up @@ -877,7 +875,7 @@ void TreeSupport::detect_overhangs(bool check_support_necessity/* = false*/)
// BBS detect sharp tail
const ExPolygons& lower_layer_sharptails = lower_layer->sharp_tails;
const auto& lower_layer_sharptails_height = lower_layer->sharp_tails_height;
for (ExPolygon& expoly : layer->lslices) {
for (ExPolygon& expoly : layer->lslices_extrudable) {
bool is_sharp_tail = false;
float accum_height = layer->height;
do {
Expand Down Expand Up @@ -907,9 +905,9 @@ void TreeSupport::detect_overhangs(bool check_support_necessity/* = false*/)
}

// 2.3 check whether sharp tail exceed the max height
for (const auto& lower_sharp_tail_height : lower_layer_sharptails_height) {
if (lower_sharp_tail_height.first->overlaps(expoly)) {
accum_height += lower_sharp_tail_height.second;
for(size_t i=0;i<lower_layer_sharptails.size();i++) {
if (lower_layer_sharptails[i].overlaps(expoly)) {
accum_height += lower_layer_sharptails_height[i];
break;
}
}
Expand All @@ -933,7 +931,7 @@ void TreeSupport::detect_overhangs(bool check_support_necessity/* = false*/)
if (is_sharp_tail) {
ExPolygons overhang = diff_ex({ expoly }, lower_layer->lslices);
layer->sharp_tails.push_back(expoly);
layer->sharp_tails_height.insert({ &expoly, accum_height });
layer->sharp_tails_height.push_back( accum_height);
append(ts_layer->overhang_areas, overhang);

if (!overhang.empty())
Expand Down

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