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Rotate instead of shear for slicing stage (#30)

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* initial commit

* fix upper bounds for assemblies

* significantly less Z shift issues, still not quite tamped down yet though

* add instrumentation to logs

* finally found the issue

* update printer defaults
This commit is contained in:
Joseph Robertson
2026-05-22 15:21:33 -05:00
committed by GitHub
parent 218881c6f6
commit a9bae54f20
16 changed files with 513 additions and 96 deletions
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src/libslic3r/PrintObjectSlice.cpp
+129 -20
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@@ -174,12 +174,15 @@ static std::vector<VolumeSlices> slice_volumes_inner(
belt_strategy->apply_to_trafo(params_base.trafo, model_volumes, has_remap, out_belt_min_z);
}
// If only remap (no belt), still need z-shift detection.
// Compose per-volume mv->get_matrix() so assembly volumes contribute their
// actual object-space positions — see the matching note in BeltSliceStrategy.
if (has_remap && !print_config.belt_printer.value) {
double min_z = std::numeric_limits<double>::max();
for (const ModelVolume *mv : model_volumes) {
if (!mv->is_model_part()) continue;
Transform3d vol_trafo = params_base.trafo * mv->get_matrix();
for (const stl_vertex &v : mv->mesh().its.vertices) {
Vec3d pt = params_base.trafo * v.cast<double>();
Vec3d pt = vol_trafo * v.cast<double>();
min_z = std::min(min_z, pt.z());
}
}
@@ -322,17 +325,35 @@ static std::vector<std::vector<ExPolygons>> slices_to_regions(
}
} else {
zs_complex.reserve(zs.size());
// region.bbox is computed in pre-belt-shear slicer space (see PrintApply.cpp::trafo_for_bbox).
// When belt transforms are active, layer Z values are in post-shear/scale/remap space,
// region.bbox is computed in pre-belt-transform slicer space (see PrintApply.cpp::trafo_for_bbox).
// When belt transforms are active, layer Z values are in post-rotation/shear/scale/remap space,
// so the Z components of region.bbox aren't comparable to z. Skipping the Z filter here
// pushes those layers into the parallel_for path below, which handles multi-volume
// clipping per layer without relying on the bbox Z range.
const bool bbox_z_in_layer_frame = !(print_config.belt_printer.value &&
(BeltTransformPipeline::has_shear(print_config)
|| BeltTransformPipeline::has_scale(print_config)
|| BeltTransformPipeline::has_rotation(print_config)
|| BeltTransformPipeline::has_preslice_remap(print_config)));
// Belt-transform addendum: with bbox-Z untrusted, the simple path's
// "first model_part wins" logic drops subsequent volumes' slices unless
// they XY-overlap with the first. Assemblies whose volumes are stacked
// or side-by-side in pre-transform Z (different bbox.z ranges) thus lose
// the volumes that originally sat outside the first volume's Z range —
// showing up as truncation at the top or bottom of the assembly. Force
// every layer in a multi-volume range through the parallel_for path,
// which correctly merges all volumes per layer.
int num_model_parts = 0;
for (const PrintObjectRegions::VolumeRegion &vr : layer_range.volume_regions)
if (vr.model_volume->is_model_part())
++num_model_parts;
const bool force_complex_for_belt = !bbox_z_in_layer_frame && num_model_parts > 1;
for (; z_idx < zs.size() && zs[z_idx] < layer_range.layer_height_range.second; ++ z_idx) {
float z = zs[z_idx];
if (force_complex_for_belt) {
zs_complex.push_back({ z_idx, z });
continue;
}
int idx_first_printable_region = -1;
bool complex = false;
for (int idx_region = 0; idx_region < int(layer_range.volume_regions.size()); ++ idx_region) {
@@ -949,7 +970,81 @@ void PrintObject::slice()
BOOST_LOG_TRIVIAL(warning) << "Belt global: object " << this->model_object()->name
<< " instances=" << this->instances().size()
<< " shift=(" << unscale<double>(inst_shift.x()) << ", " << unscale<double>(inst_shift.y()) << ")";
double global_z_offset = 0.;
// Per-object Z-shift compensation, applied regardless of global mode.
//
// BeltSliceStrategy::apply_to_trafo lifts the mesh by max(0, -m_belt_min_z)
// so the slicer can slice with slicer_z >= 0. BeltBackTransform inverts
// build_forward_transform() which DOES NOT include this per-object
// Z-shift (it's not known until vertex scan time). Result: G-code
// coords emerge offset by the un-undone Z-shift — for shear that's a
// pure machine_z lift; for rotation it leaks into both machine_y and
// machine_z because the inverse rotation couples slicer_z back into
// both axes. Compensating layer.print_z by shear_min_z here makes the
// back-transform produce correct machine-frame coordinates whether or
// not any global mode is active.
//
// (The original global-mode-only application of shear_min_z was sized
// for cube-vs-inverted-cone-tip differentiation; the same compensation
// is what fixes assemblies and rotation-mode parts where z_shift > 0.)
double belt_surface_z = BeltTransformPipeline::has_preslice_remap(pcfg)
? BeltTransformPipeline::remap_bbox(*this->model_object(), pcfg).min.z() : 0.;
double shear_min_z = m_belt_min_z - belt_surface_z;
double global_z_offset = shear_min_z;
// Centering correction: trafo_centered pretranslates by
// -m_center_offset.{x,y}. Under the belt forward transform, the
// Y component of that pretranslate couples into slicer-Z (shear:
// tan*c.y, rotation: sin*c.y). BeltBackTransform inverts the
// rotation/shear but doesn't undo centering, so this Z component
// leaks into machine output as a position offset whenever
// m_center_offset != 0. When a user moves a volume within an
// assembly such that the combined bbox center shifts, this shows
// up as a small Z translation in the print. Compensate by adding
// the Z component of the centering through the forward transform.
{
Transform3d T_fwd = BeltTransformPipeline::build_forward_transform(pcfg);
Vec3d c_off(unscale<double>(m_center_offset.x()),
unscale<double>(m_center_offset.y()),
0.);
double centering_z_corr = (T_fwd.linear() * c_off).z();
global_z_offset += centering_z_corr;
BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] centering correction"
<< " obj=" << this->model_object()->name
<< " m_center_offset_mm=(" << c_off.x() << "," << c_off.y() << ")"
<< " centering_z_corr=" << centering_z_corr
<< " (added to global_z_offset)";
}
// [BELT-DEBUG] Per-object summary so Case A vs Case B can be compared
// side-by-side. Lays out every value that feeds into the final layer
// print_z adjustment.
{
BoundingBoxf3 raw_bb = this->model_object()->raw_bounding_box();
BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] slice() per-object summary"
<< " obj=" << this->model_object()->name
<< " n_volumes=" << this->model_object()->volumes.size()
<< " raw_bbox.min=(" << raw_bb.min.x() << "," << raw_bb.min.y() << "," << raw_bb.min.z() << ")"
<< " raw_bbox.max=(" << raw_bb.max.x() << "," << raw_bb.max.y() << "," << raw_bb.max.z() << ")"
<< " raw_bbox.center=(" << raw_bb.center().x() << "," << raw_bb.center().y() << ")"
<< " m_center_offset=(" << unscale<double>(m_center_offset.x()) << "," << unscale<double>(m_center_offset.y()) << ")"
<< " inst_shift=(" << unscale<double>(inst_shift.x()) << "," << unscale<double>(inst_shift.y()) << ")"
<< " m_belt_min_z=" << m_belt_min_z
<< " belt_surface_z=" << belt_surface_z
<< " shear_min_z=" << shear_min_z;
// Per-volume bbox + get_matrix translation so order/composition is visible.
int vi = 0;
for (const ModelVolume *mv : this->model_object()->volumes) {
if (!mv->is_model_part()) { ++vi; continue; }
BoundingBoxf3 vol_bb = mv->mesh().transformed_bounding_box(mv->get_matrix());
BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] vol[" << vi
<< "] id=" << mv->id().id << " name='" << mv->name << "'"
<< " get_matrix.translation=(" << mv->get_matrix().translation().x() << "," << mv->get_matrix().translation().y() << "," << mv->get_matrix().translation().z() << ")"
<< " object_bbox.min=(" << vol_bb.min.x() << "," << vol_bb.min.y() << "," << vol_bb.min.z() << ")"
<< " object_bbox.max=(" << vol_bb.max.x() << "," << vol_bb.max.y() << "," << vol_bb.max.z() << ")";
++vi;
}
}
if (pcfg.belt_preslice_global.value) {
// Global pre-slice mode: compute full correction c = (T.linear() - I) * d
@@ -957,18 +1052,7 @@ void PrintObject::slice()
Transform3d T = BeltTransformPipeline::build_forward_transform(pcfg);
Vec3d d(unscale<double>(inst_shift.x()), unscale<double>(inst_shift.y()), 0.);
Vec3d c = T.linear() * d - d;
// Per-object shape contribution: BeltSliceStrategy::apply_to_trafo
// lifts the mesh by max(0, -m_belt_min_z) to keep slicer-frame Z
// above 0. Two objects at the same bed position but different
// m_belt_min_z (e.g. cube vs inverted-cone tip) otherwise end up
// at the same print_z, which causes the inverted-cone tip to
// start on the same layer as the cube's lowest sheared corner.
double belt_surface_z = BeltTransformPipeline::has_preslice_remap(pcfg)
? BeltTransformPipeline::remap_bbox(*this->model_object(), pcfg).min.z() : 0.;
double shear_min_z = m_belt_min_z - belt_surface_z;
global_z_offset = c.z() + shear_min_z;
global_z_offset += c.z();
BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] write m_belt_global_xy_correction tid=" << std::this_thread::get_id()
<< " obj=" << this << " old=(" << m_belt_global_xy_correction.x() << "," << m_belt_global_xy_correction.y()
<< ") new=(" << c.x() << "," << c.y() << ")";
@@ -999,10 +1083,7 @@ void PrintObject::slice()
Transform3d T = BeltTransformPipeline::build_forward_transform(pcfg);
Vec3d d(unscale<double>(inst_shift.x()), unscale<double>(inst_shift.y()), 0.);
Vec3d c = T.linear() * d - d;
double belt_surface_z = BeltTransformPipeline::has_preslice_remap(pcfg)
? BeltTransformPipeline::remap_bbox(*this->model_object(), pcfg).min.z() : 0.;
double shear_min_z = m_belt_min_z - belt_surface_z;
global_z_offset += c.z() + shear_min_z;
global_z_offset += c.z();
BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] write m_belt_global_xy_correction tid=" << std::this_thread::get_id()
<< " obj=" << this << " old=(" << m_belt_global_xy_correction.x() << "," << m_belt_global_xy_correction.y()
<< ") new=(" << c.x() << "," << c.y() << ")";
@@ -1012,6 +1093,19 @@ void PrintObject::slice()
<< " shear_min_z=" << shear_min_z << " (m_belt_min_z=" << m_belt_min_z << ")";
}
// Slicing rotation in global mode: bed-position-dependent Z offset.
// For R(α, X): c.z = sin(α)*d.y so objects at different bed-Y
// values print at different machine Z values along the inclined belt.
if (pcfg.belt_slice_rotation_global.value
&& pcfg.belt_slice_rotation.value != BeltRotationAxis::None
&& std::abs(pcfg.belt_slice_rotation_angle.value) > EPSILON) {
Transform3d T = BeltTransformPipeline::build_forward_transform(pcfg);
Vec3d d(unscale<double>(inst_shift.x()), unscale<double>(inst_shift.y()), 0.);
Vec3d c = T.linear() * d - d;
global_z_offset += c.z();
m_belt_global_xy_correction = Vec2d(c.x(), c.y());
}
// Pre-slice remap global mode: when on, the remap accounts for the
// instance bed position. The Z component of the correction
// (R - I) * d shifts layer print_z so e.g. a Y↔Z swap with an
@@ -1030,6 +1124,15 @@ void PrintObject::slice()
BOOST_LOG_TRIVIAL(warning) << "[BELTRACE] write m_belt_global_z_offset tid=" << std::this_thread::get_id()
<< " obj=" << this << " old=" << m_belt_global_z_offset << " new=" << global_z_offset;
m_belt_global_z_offset = global_z_offset;
// [BELT-DEBUG] Final breakdown of all contributions to layer.print_z
// and where the first / last layer end up post-adjustment.
BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] global_z_offset breakdown"
<< " obj=" << this->model_object()->name
<< " shear_min_z=" << shear_min_z
<< " total_global_z_offset=" << global_z_offset
<< " xy_correction=(" << m_belt_global_xy_correction.x() << "," << m_belt_global_xy_correction.y() << ")"
<< " belt_floor_z_shift_before=" << (m_slicing_params.belt_floor_z_shift)
<< " n_layers=" << m_layers.size();
if (std::abs(global_z_offset) > EPSILON) {
for (Layer *layer : m_layers)
layer->print_z += global_z_offset;
@@ -1038,6 +1141,12 @@ void PrintObject::slice()
// layer print_z, so belt_floor_z_shift must match.
m_slicing_params.belt_floor_z_shift += global_z_offset;
}
if (!m_layers.empty()) {
BOOST_LOG_TRIVIAL(warning) << "[BELT-DEBUG] post-adjustment"
<< " first_layer.print_z=" << m_layers.front()->print_z
<< " last_layer.print_z=" << m_layers.back()->print_z
<< " belt_floor_z_shift_after=" << m_slicing_params.belt_floor_z_shift;
}
if (!m_layers.empty()) {
BOOST_LOG_TRIVIAL(warning) << "Belt global: first_layer_z=" << m_layers.front()->print_z
<< " last_layer_z=" << m_layers.back()->print_z