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[CURA-13266] Skin-support: No more infill-bridging over skin one layer lower. #2363

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Merged
HellAholic merged 4 commits into from
Aug 20, 2026
+78 −51
Merged

[CURA-13266] Skin-support: No more infill-bridging over skin one layer lower. #2363

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9f16a4f
Skin-support: No more infill-bridging over skin one layer lower.
rburema Aug 13, 2026
be68ac1
Apply clang-format
rburema Aug 13, 2026
aa2e191
Break-out local closure to full member function.
rburema Aug 18, 2026
cda787e
Merge branch 'main' into CURA-13266_skip_1_layer_infill_support_better
HellAholic Aug 20, 2026
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12 changes: 12 additions & 0 deletions include/FffGcodeWriter.h
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Original file line number Diff line number Diff line change
Expand Up @@ -743,6 +743,16 @@ class FffGcodeWriter : public NoCopy
*/
unsigned int findSpiralizedLayerSeamVertexIndex(const SliceDataStorage& storage, const SliceMeshStorage& mesh, const int layer_nr, const int last_layer_nr);

/*!
* Retrieve all skin relevant to skin support from the indicated layer w.r.t. the indicated part (on an adjacent layer).
*
* \param skin_combined [out] Return parameter.
* \param mesh [in] Relevant mesh.
* \param part [in] The part that we're currently checking.
* \param skin_layer_nr [in] A layer that is adjacent to the part (so either above or below the layer of the part).
*/
static void getCombinedSkinForSkinSupport(Shape& skin_combined, const SliceMeshStorage& mesh, const SliceLayerPart& part, int skin_layer_nr);

/*!
* Partition the Infill regions by the skin at N layers above.
*
Expand All @@ -753,6 +763,7 @@ class FffGcodeWriter : public NoCopy
*
* \param infill_below_skin [out] Polygons with infill below the skin
* \param infill_not_below_skin [out] Polygons with infill outside of skin regions above
* \param infill_sandwiched [out] Polygons with infill that both has regions of skin both above _and_ below
* \param gcode_layer The initial planning of the gcode of the layer
* \param mesh the mesh containing the layer of interest
* \param part \param part The part for which to create gcode
Expand All @@ -761,6 +772,7 @@ class FffGcodeWriter : public NoCopy
static void partitionInfillBySkinAbove(
Shape& infill_below_skin,
Shape& infill_not_below_skin,
Shape& infill_sandwiched,
const LayerPlan& gcode_layer,
const SliceMeshStorage& mesh,
const SliceLayerPart& part,
Expand Down
117 changes: 66 additions & 51 deletions src/FffGcodeWriter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2173,10 +2173,11 @@ bool FffGcodeWriter::processSingleLayerInfill(
// boundary edge
Shape infill_below_skin;
Shape infill_not_below_skin;
Shape infill_sandwiched;
AngleDegrees skin_support_angle;
if (gcode_layer.getLayerNr() > 0)
{
partitionInfillBySkinAbove(infill_below_skin, infill_not_below_skin, gcode_layer, mesh, part, infill_line_width);
partitionInfillBySkinAbove(infill_below_skin, infill_not_below_skin, infill_sandwiched, gcode_layer, mesh, part, infill_line_width);
}

if (! infill_below_skin.empty())
Expand All @@ -2185,7 +2186,8 @@ bool FffGcodeWriter::processSingleLayerInfill(
const coord_t infill_wall_offset = -infill_wall_line_count * infill_line_width;
const Shape infill_contour = part.infill_area.offset(-(infill_line_width / 2) + infill_overlap + infill_wall_offset);
const LayerPlan* completed_layer_below = layer_plan_buffer.getCompletedLayerPlan(gcode_layer.getLayerNr() - 1);
std::tie(infill_below_skin, skin_support_angle) = makeBridgeOverInfillPrintable(infill_contour, infill_below_skin, mesh, completed_layer_below, gcode_layer.getLayerNr());
std::tie(infill_below_skin, skin_support_angle)
= makeBridgeOverInfillPrintable(infill_contour.difference(infill_sandwiched), infill_below_skin, mesh, completed_layer_below, gcode_layer.getLayerNr());
infill_not_below_skin = infill_not_below_skin.difference(infill_below_skin);
}

Expand Down Expand Up @@ -2417,75 +2419,88 @@ bool FffGcodeWriter::processSingleLayerInfill(
return added_something;
}

void FffGcodeWriter::partitionInfillBySkinAbove(
Shape& infill_below_skin,
Shape& infill_not_below_skin,
const LayerPlan& gcode_layer,
const SliceMeshStorage& mesh,
const SliceLayerPart& part,
coord_t infill_line_width)
void FffGcodeWriter::getCombinedSkinForSkinSupport(Shape& skin_combined, const SliceMeshStorage& mesh, const SliceLayerPart& part, int skin_layer_nr)
{
constexpr coord_t tiny_infill_offset = 20;
const bool skin_support = mesh.settings.get<bool>("skin_support");

if (! skin_support)
if (skin_layer_nr >= mesh.layers.size() || skin_layer_nr < 1)
{
return;
}

Shape skin_above_combined; // skin regions on the layers above combined with small gaps between

const size_t skin_layer_nr = gcode_layer.getLayerNr() + 1;
if (skin_layer_nr < mesh.layers.size())
for (const SliceLayerPart& part_i : mesh.layers[skin_layer_nr].parts)
{
for (const SliceLayerPart& part_i : mesh.layers[skin_layer_nr].parts)
for (const SkinPart& skin_part : part_i.skin_parts)
{
for (const SkinPart& skin_part : part_i.skin_parts)
{
// Limit considered areas to the ones that should have infill underneath at the current layer.
const Shape relevant_outline = skin_part.outline.intersection(part.getOwnInfillArea());
// Limit considered areas to the ones that should have infill underneath at the current layer.
const Shape relevant_outline = skin_part.outline.intersection(part.getOwnInfillArea());

if (! skin_above_combined.empty())
if (! skin_combined.empty())
{
// does this skin part overlap with any of the skin parts on the layers above?
const Shape overlap = skin_combined.intersection(relevant_outline);
if (! overlap.empty())
{
// does this skin part overlap with any of the skin parts on the layers above?
const Shape overlap = skin_above_combined.intersection(relevant_outline);
if (! overlap.empty())
{
// yes, it overlaps, need to leave a gap between this skin part and the others
// add this layer's skin region without subtracting the overlap but still make a gap between this skin region and what has been accumulated so
// far we do this so that these skin region edges will definitely have infill walls below them

// looking from the side, if the combined regions so far look like this...
//
// ----------------------------------
//
// and the new skin part looks like this...
//
// -------------------------------------
//
// the result should be like this...
//
// ------- -------------------------------------

skin_above_combined = skin_above_combined.difference(relevant_outline.offset(tiny_infill_offset));
skin_above_combined.push_back(relevant_outline);
}
else // no overlap
{
skin_above_combined.push_back(relevant_outline);
}
// yes, it overlaps, need to leave a gap between this skin part and the others
// add this layer's skin region without subtracting the overlap but still make a gap between this skin region and what has been accumulated so
// far we do this so that these skin region edges will definitely have infill walls below them

// looking from the side, if the combined regions so far look like this...
//
// ----------------------------------
//
// and the new skin part looks like this...
//
// -------------------------------------
//
// the result should be like this...
//
// ------- -------------------------------------

skin_combined = skin_combined.difference(relevant_outline.offset(tiny_infill_offset));
skin_combined.push_back(relevant_outline);
}
else // this is the first skin region we have looked at
else // no overlap
{
skin_above_combined.push_back(relevant_outline);
skin_combined.push_back(relevant_outline);
}
}
else // this is the first skin region we have looked at
{
skin_combined.push_back(relevant_outline);
}
}
}
}

void FffGcodeWriter::partitionInfillBySkinAbove(
Shape& infill_below_skin,
Shape& infill_not_below_skin,
Shape& infill_sandwiched,
const LayerPlan& gcode_layer,
const SliceMeshStorage& mesh,
const SliceLayerPart& part,
coord_t infill_line_width)
{
const bool skin_support = mesh.settings.get<bool>("skin_support");

if (! skin_support)
{
return;
}

Shape skin_above_combined; // skin regions on the layers above combined with small gaps between
Shape skin_below_combined; // same for the skin below (to check if we're sandwiching only 1 layer of infill, in which case we shouldn't do the support)
getCombinedSkinForSkinSupport(skin_above_combined, mesh, part, gcode_layer.getLayerNr() + 1);
getCombinedSkinForSkinSupport(skin_below_combined, mesh, part, std::max(LayerIndex{ 1 }, gcode_layer.getLayerNr()) - 1);
infill_sandwiched = skin_above_combined.intersection(skin_below_combined);

// the shrink/expand here is to remove regions of infill below skin that are narrower than the width of the infill walls otherwise the infill walls could merge and form
// a bump
infill_below_skin = skin_above_combined.intersection(part.infill_area_per_combine_per_density.back().front()).offset(-infill_line_width).offset(infill_line_width);
infill_below_skin = skin_above_combined.difference(skin_below_combined)
.intersection(part.infill_area_per_combine_per_density.back().front())
.offset(-infill_line_width)
.offset(infill_line_width);

constexpr bool remove_small_holes_from_infill_below_skin = true;
constexpr double min_area_multiplier = 25;
Expand Down
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