WIP: Transformation of instances in world coordinate space:

Ulocking the "anisotropic" scaling checkbox will bake the transformation
into meshes to allow for scaling in world axes.

Optimized and templated the stl_transform functions, now also available for 3x3 matrices.
The Canvas3D::reload_scene() now maintains selection even if all volumes of an instance changed their IDs.

src/libslic3r/Geometry.hpp

@@ -269,6 +269,21 @@ extern Eigen::Quaterniond rotation_xyz_diff(const Vec3d &rot_xyz_from, const Vec
 // This should only be called if it is known, that the two rotations only differ in rotation around the Z axis.
 extern double rotation_diff_z(const Vec3d &rot_xyz_from, const Vec3d &rot_xyz_to);
 
+// Is the angle close to a multiple of 90 degrees?
+inline bool is_rotation_ninety_degrees(double a)
+{
+    a = fmod(std::abs(a), 0.5 * M_PI);
+    if (a > 0.25 * PI)
+        a = 0.5 * PI - a;
+    return a < 0.001;
+}
+
+// Is the angle close to a multiple of 90 degrees?
+inline bool is_rotation_ninety_degrees(const Vec3d &rotation)
+{
+    return is_rotation_ninety_degrees(rotation.x()) && is_rotation_ninety_degrees(rotation.y()) && is_rotation_ninety_degrees(rotation.z());
+}
+
 } }
 
 #endif

src/libslic3r/Model.cpp

@@ -24,6 +24,19 @@ unsigned int Model::s_auto_extruder_id = 1;
 
 size_t ModelBase::s_last_id = 0;
 
+// Unique object / instance ID for the wipe tower.
+ModelID wipe_tower_object_id()
+{
+    static ModelBase mine;
+    return mine.id();
+}
+
+ModelID wipe_tower_instance_id()
+{
+    static ModelBase mine;
+    return mine.id();
+}
+
 Model& Model::assign_copy(const Model &rhs)
 {
     this->copy_id(rhs);
@@ -1320,6 +1333,58 @@ void ModelObject::repair()
         v->mesh.repair();
 }
 
+// Support for non-uniform scaling of instances. If an instance is rotated by angles, which are not multiples of ninety degrees,
+// then the scaling in world coordinate system is not representable by the Geometry::Transformation structure.
+// This situation is solved by baking in the instance transformation into the mesh vertices.
+// Rotation and mirroring is being baked in. In case the instance scaling was non-uniform, it is baked in as well.
+void ModelObject::bake_xy_rotation_into_meshes(size_t instance_idx)
+{
+    assert(instance_idx < this->instances.size());
+
+	const Geometry::Transformation reference_trafo = this->instances[instance_idx]->get_transformation();
+    if (Geometry::is_rotation_ninety_degrees(reference_trafo.get_rotation()))
+        // nothing to do, scaling in the world coordinate space is possible in the representation of Geometry::Transformation.
+        return;
+
+    bool   left_handed        = reference_trafo.is_left_handed();
+    bool   has_mirrorring     = ! reference_trafo.get_mirror().isApprox(Vec3d(1., 1., 1.));
+    bool   uniform_scaling    = std::abs(reference_trafo.get_scaling_factor().x() - reference_trafo.get_scaling_factor().y()) < EPSILON &&
+                                std::abs(reference_trafo.get_scaling_factor().x() - reference_trafo.get_scaling_factor().z()) < EPSILON;
+    double new_scaling_factor = uniform_scaling ? reference_trafo.get_scaling_factor().x() : 1.;
+
+    // Adjust the instances.
+    for (size_t i = 0; i < this->instances.size(); ++ i) {
+        ModelInstance &model_instance = *this->instances[i];
+        model_instance.set_rotation(Vec3d(0., 0., Geometry::rotation_diff_z(reference_trafo.get_rotation(), model_instance.get_rotation())));
+        model_instance.set_scaling_factor(Vec3d(new_scaling_factor, new_scaling_factor, new_scaling_factor));
+        model_instance.set_mirror(Vec3d(1., 1., 1.));
+    }
+
+    // Adjust the meshes.
+    // Transformation to be applied to the meshes.
+    Eigen::Matrix3d    mesh_trafo_3x3           = reference_trafo.get_matrix(true, false, uniform_scaling, ! has_mirrorring).matrix().block<3, 3>(0, 0);
+	Transform3d volume_offset_correction = this->instances[instance_idx]->get_transformation().get_matrix().inverse() * reference_trafo.get_matrix();
+    for (ModelVolume *model_volume : this->volumes) {
+        const Geometry::Transformation volume_trafo = model_volume->get_transformation();
+        bool   volume_left_handed        = volume_trafo.is_left_handed();
+        bool   volume_has_mirrorring     = ! volume_trafo.get_mirror().isApprox(Vec3d(1., 1., 1.));
+        bool   volume_uniform_scaling    = std::abs(volume_trafo.get_scaling_factor().x() - volume_trafo.get_scaling_factor().y()) < EPSILON &&
+                                           std::abs(volume_trafo.get_scaling_factor().x() - volume_trafo.get_scaling_factor().z()) < EPSILON;
+        double volume_new_scaling_factor = volume_uniform_scaling ? volume_trafo.get_scaling_factor().x() : 1.;
+        // Transform the mesh.
+		Matrix3d volume_trafo_3x3 = volume_trafo.get_matrix(true, false, volume_uniform_scaling, !volume_has_mirrorring).matrix().block<3, 3>(0, 0);
+		model_volume->transform_mesh(mesh_trafo_3x3 * volume_trafo_3x3, left_handed != volume_left_handed);
+        // Reset the rotation, scaling and mirroring.
+        model_volume->set_rotation(Vec3d(0., 0., 0.));
+        model_volume->set_scaling_factor(Vec3d(volume_new_scaling_factor, volume_new_scaling_factor, volume_new_scaling_factor));
+        model_volume->set_mirror(Vec3d(1., 1., 1.));
+        // Move the reference point of the volume to compensate for the change of the instance trafo.
+        model_volume->set_offset(volume_offset_correction * volume_trafo.get_offset());
+    }
+
+    this->invalidate_bounding_box();
+}
+
 double ModelObject::get_min_z() const
 {
     if (instances.empty())
@@ -1656,6 +1721,22 @@ void ModelVolume::scale_geometry(const Vec3d& versor)
     m_convex_hull.scale(versor);
 }
 
+void ModelVolume::transform_mesh(const Transform3d &mesh_trafo, bool fix_left_handed)
+{
+    this->mesh.transform(mesh_trafo, fix_left_handed);
+    this->m_convex_hull.transform(mesh_trafo, fix_left_handed);
+    // Let the rest of the application know that the geometry changed, so the meshes have to be reloaded.
+    this->set_new_unique_id();
+}
+
+void ModelVolume::transform_mesh(const Matrix3d &matrix, bool fix_left_handed)
+{
+	this->mesh.transform(matrix, fix_left_handed);
+	this->m_convex_hull.transform(matrix, fix_left_handed);
+    // Let the rest of the application know that the geometry changed, so the meshes have to be reloaded.
+    this->set_new_unique_id();
+}
+
 void ModelInstance::transform_mesh(TriangleMesh* mesh, bool dont_translate) const
 {
     mesh->transform(get_matrix(dont_translate));

src/libslic3r/Model.hpp

@@ -54,6 +54,10 @@ struct ModelID
 	size_t	id;
 };
 
+// Unique object / instance ID for the wipe tower.
+extern ModelID wipe_tower_object_id();
+extern ModelID wipe_tower_instance_id();
+
 // Base for Model, ModelObject, ModelVolume, ModelInstance or ModelMaterial to provide a unique ID
 // to synchronize the front end (UI) with the back end (BackgroundSlicingProcess / Print / PrintObject).
 // Achtung! The s_last_id counter is not thread safe, so it is expected, that the ModelBase derived instances
@@ -85,6 +89,9 @@ private:
 
 	static inline ModelID   generate_new_id() { return ModelID(++ s_last_id); }
     static size_t           s_last_id;
+	
+	friend ModelID wipe_tower_object_id();
+	friend ModelID wipe_tower_instance_id();
 };
 
 #define MODELBASE_DERIVED_COPY_MOVE_CLONE(TYPE) \
@@ -265,6 +272,11 @@ public:
     ModelObjectPtrs cut(size_t instance, coordf_t z, bool keep_upper = true, bool keep_lower = true, bool rotate_lower = false);    // Note: z is in world coordinates
     void split(ModelObjectPtrs* new_objects);
     void repair();
+    // Support for non-uniform scaling of instances. If an instance is rotated by angles, which are not multiples of ninety degrees,
+    // then the scaling in world coordinate system is not representable by the Geometry::Transformation structure.
+    // This situation is solved by baking in the instance transformation into the mesh vertices.
+    // Rotation and mirroring is being baked in. In case the instance scaling was non-uniform, it is baked in as well.
+    void bake_xy_rotation_into_meshes(size_t instance_idx);
 
     double get_min_z() const;
     double get_instance_min_z(size_t instance_idx) const;
@@ -414,6 +426,8 @@ protected:
 
 	explicit ModelVolume(const ModelVolume &rhs) = default;
     void     set_model_object(ModelObject *model_object) { object = model_object; }
+    void     transform_mesh(const Transform3d& t, bool fix_left_handed);
+    void     transform_mesh(const Matrix3d& m, bool fix_left_handed);
 
 private:
     // Parent object owning this ModelVolume.

src/libslic3r/Point.hpp

@@ -40,6 +40,11 @@ typedef std::vector<Vec3crd>                            Points3;
 typedef std::vector<Vec2d>                              Pointfs;
 typedef std::vector<Vec3d>                              Pointf3s;
 
+typedef Eigen::Matrix<float,  2, 2, Eigen::DontAlign> Matrix2f;
+typedef Eigen::Matrix<double, 2, 2, Eigen::DontAlign> Matrix2d;
+typedef Eigen::Matrix<float,  3, 3, Eigen::DontAlign> Matrix3f;
+typedef Eigen::Matrix<double, 3, 3, Eigen::DontAlign> Matrix3d;
+
 typedef Eigen::Transform<float,  2, Eigen::Affine, Eigen::DontAlign> Transform2f;
 typedef Eigen::Transform<double, 2, Eigen::Affine, Eigen::DontAlign> Transform2d;
 typedef Eigen::Transform<float,  3, Eigen::Affine, Eigen::DontAlign> Transform3f;

src/libslic3r/TriangleMesh.cpp

@@ -330,6 +330,17 @@ void TriangleMesh::transform(const Transform3d& t, bool fix_left_handed)
 	}
 }
 
+void TriangleMesh::transform(const Matrix3d& m, bool fix_left_handed)
+{
+    stl_transform(&stl, m);
+    stl_invalidate_shared_vertices(&stl);
+    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.
+        this->repair();
+        stl_reverse_all_facets(&stl);
+    }
+}
+
 void TriangleMesh::align_to_origin()
 {
     this->translate(

src/libslic3r/TriangleMesh.hpp

@@ -52,6 +52,7 @@ public:
     void mirror_y() { this->mirror(Y); }
     void mirror_z() { this->mirror(Z); }
     void transform(const Transform3d& t, bool fix_left_handed = false);
+	void transform(const Matrix3d& t, bool fix_left_handed = false);
     void align_to_origin();
     void rotate(double angle, Point* center);
     TriangleMeshPtrs split() const;