Fix normal direction when exporting STL (#6406)

The export function does not depend on Model/ModelObject::mesh() family of functions, changing them might break the already too brittle code.
prusa3d · Apr 26, 2021 · 978b359 · 978b359
1 parent d1cfdcb
commit 978b359
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Showing 6 changed files with 42 additions and 26 deletions.
diff --git a/src/libslic3r/Model.cpp b/src/libslic3r/Model.cpp
@@ -833,18 +833,6 @@ indexed_triangle_set ModelObject::raw_indexed_triangle_set() const
  return out;
 }
 
-// Non-transformed (non-rotated, non-scaled, non-translated) sum of all object volumes.
-TriangleMesh ModelObject::full_raw_mesh() const
-{
- TriangleMesh mesh;
- for (const ModelVolume *v : this->volumes)
- {
- TriangleMesh vol_mesh(v->mesh());
- vol_mesh.transform(v->get_matrix());
- mesh.merge(vol_mesh);
- }
- return mesh;
-}
 
 const BoundingBoxf3& ModelObject::raw_mesh_bounding_box() const
 {

diff --git a/src/libslic3r/Model.hpp b/src/libslic3r/Model.hpp
@@ -289,8 +289,6 @@ class ModelObject final : public ObjectBase
  TriangleMesh raw_mesh() const;
  // The same as above, but producing a lightweight indexed_triangle_set.
  indexed_triangle_set raw_indexed_triangle_set() const;
- // Non-transformed (non-rotated, non-scaled, non-translated) sum of all object volumes.
- TriangleMesh full_raw_mesh() const;
  // A transformed snug bounding box around the non-modifier object volumes, without the translation applied.
  // This bounding box is only used for the actual slicing.
  const BoundingBoxf3& raw_bounding_box() const;

diff --git a/src/libslic3r/PrintObject.cpp b/src/libslic3r/PrintObject.cpp
@@ -2207,6 +2207,7 @@ std::vector<ExPolygons> PrintObject::slice_volumes(
  TriangleMesh vol_mesh(model_volume.mesh());
  vol_mesh.transform(model_volume.get_matrix(), true);
  mesh.merge(vol_mesh);
+ mesh.repair(false);
  }
  if (mesh.stl.stats.number_of_facets > 0) {
  mesh.transform(m_trafo, true);

diff --git a/src/libslic3r/TriangleMesh.cpp b/src/libslic3r/TriangleMesh.cpp
@@ -357,10 +357,14 @@ void TriangleMesh::transform(const Transform3d& t, bool fix_left_handed)
  its_transform(its, t);
  if (fix_left_handed && t.matrix().block(0, 0, 3, 3).determinant() < 0.) {
  // Left handed transformation is being applied. It is a good idea to flip the faces and their normals.
- this->repair(false);
- stl_reverse_all_facets(&stl);
- this->its.clear();
- this->require_shared_vertices();
+ // As for the assert: the repair function would fix the normals, reversing would
+ // break them again. The caller should provide a mesh that does not need repair.
+ // The repair call is left here so things don't break more than they were.
+ assert(this->repaired);
+ this->repair(false);
+ stl_reverse_all_facets(&stl);
+ this->its.clear();
+ this->require_shared_vertices();
  }
 }
 
@@ -369,11 +373,12 @@ void TriangleMesh::transform(const Matrix3d& m, bool fix_left_handed)
  stl_transform(&stl, m);
  its_transform(its, m);
  if (fix_left_handed && m.determinant() < 0.) {
- // Left handed transformation is being applied. It is a good idea to flip the faces and their normals.
+ // See comments in function above.
+ assert(this->repaired);
  this->repair(false);
  stl_reverse_all_facets(&stl);
- this->its.clear();
- this->require_shared_vertices();
+ this->its.clear();
+ this->require_shared_vertices();
  }
 }
 

diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -1,7 +1,6 @@
 #include "libslic3r/libslic3r.h"
 #include "GLCanvas3D.hpp"
 
-#include "admesh/stl.h"
 #include "libslic3r/ClipperUtils.hpp"
 #include "libslic3r/PrintConfig.hpp"
 #include "libslic3r/GCode/ThumbnailData.hpp"

diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
@@ -5085,27 +5085,52 @@ void Plater::export_stl(bool extended, bool selection_only)
  if (selection_only && (obj_idx == -1 || selection.is_wipe_tower()))
  return;
 
+ // Following lambda generates a combined mesh for export with normals pointing outwards.
+ auto mesh_to_export = [](const ModelObject* mo, bool instances) -> TriangleMesh {
+ TriangleMesh mesh;
+ for (const ModelVolume *v : mo->volumes)
+ if (v->is_model_part()) {
+ TriangleMesh vol_mesh(v->mesh());
+ vol_mesh.repair();
+ vol_mesh.transform(v->get_matrix(), true);
+ mesh.merge(vol_mesh);
+ }
+ mesh.repair();
+ if (instances) {
+ TriangleMesh vols_mesh(mesh);
+ mesh = TriangleMesh();
+ for (const ModelInstance *i : mo->instances) {
+ TriangleMesh m = vols_mesh;
+ m.transform(i->get_matrix(), true);
+ mesh.merge(m);
+ }
+ }
+ mesh.repair();
+ return mesh;
+ };
+
  TriangleMesh mesh;
  if (p->printer_technology == ptFFF) {
  if (selection_only) {
  const ModelObject* model_object = p->model.objects[obj_idx];
  if (selection.get_mode() == Selection::Instance)
  {
  if (selection.is_single_full_object())
- mesh = model_object->mesh();
+ mesh = mesh_to_export(model_object, true);
  else
- mesh = model_object->full_raw_mesh();
+ mesh = mesh_to_export(model_object, false);
  }
  else
  {
  const GLVolume* volume = selection.get_volume(*selection.get_volume_idxs().begin());
  mesh = model_object->volumes[volume->volume_idx()]->mesh();
- mesh.transform(volume->get_volume_transformation().get_matrix());
+ mesh.transform(volume->get_volume_transformation().get_matrix(), true);
  mesh.translate(-model_object->origin_translation.cast<float>());
  }
  }
  else {
- mesh = p->model.mesh();
+ for (const ModelObject *o : p->model.objects)
+ mesh.merge(mesh_to_export(o, true));
  }
  }
  else