PrusaSlicer-NonPlainar/xs/src/libslic3r/Model.cpp

#include "Model.hpp"
#include "Geometry.hpp"

namespace Slic3r {

Model::Model(const Model &other)
{
    // copy materials
    for (const auto &m : other.materials)
        this->add_material(m.first, *m.second);
    // copy objects
    this->objects.reserve(other.objects.size());
    for (const ModelObject *o : other.objects)
        this->add_object(*o, true);
}

Model& Model::operator=(Model other)
{
    this->swap(other);
    return *this;
}

void Model::swap(Model &other)
{
    std::swap(this->materials,  other.materials);
    std::swap(this->objects,    other.objects);
}

Model::~Model()
{
    this->clear_objects();
    this->clear_materials();
}

ModelObject* Model::add_object()
{
    this->objects.emplace_back(new ModelObject(this));
    return this->objects.back();
}

ModelObject* Model::add_object(const char *name, const char *path, const TriangleMesh &mesh)
{
    ModelObject* new_object = new ModelObject(this);
    this->objects.push_back(new_object);
    new_object->name = name;
    new_object->input_file = path;
    ModelVolume *new_volume = new_object->add_volume(mesh);
    new_volume->name = name;
    new_object->invalidate_bounding_box();
    return new_object;
}

ModelObject* Model::add_object(const char *name, const char *path, TriangleMesh &&mesh)
{
    ModelObject* new_object = new ModelObject(this);
    this->objects.push_back(new_object);
    new_object->name = name;
    new_object->input_file = path;
    ModelVolume *new_volume = new_object->add_volume(std::move(mesh));
    new_volume->name = name;
    new_object->invalidate_bounding_box();
    return new_object;
}

ModelObject* Model::add_object(const ModelObject &other, bool copy_volumes)
{
    ModelObject* new_object = new ModelObject(this, other, copy_volumes);
    this->objects.push_back(new_object);
    return new_object;
}

void Model::delete_object(size_t idx)
{
    ModelObjectPtrs::iterator i = this->objects.begin() + idx;
    delete *i;
    this->objects.erase(i);
}

void Model::clear_objects()
{
    for (ModelObject *o : this->objects)
        delete o;
    this->objects.clear();
}

void Model::delete_material(t_model_material_id material_id)
{
    ModelMaterialMap::iterator i = this->materials.find(material_id);
    if (i != this->materials.end()) {
        delete i->second;
        this->materials.erase(i);
    }
}

void Model::clear_materials()
{
    for (auto &m : this->materials)
        delete m.second;
    this->materials.clear();
}

ModelMaterial* Model::add_material(t_model_material_id material_id)
{
    ModelMaterial* material = this->get_material(material_id);
    if (material == nullptr)
        material = this->materials[material_id] = new ModelMaterial(this);
    return material;
}

ModelMaterial* Model::add_material(t_model_material_id material_id, const ModelMaterial &other)
{
    // delete existing material if any
    ModelMaterial* material = this->get_material(material_id);
    delete material;
    // set new material
    material = new ModelMaterial(this, other);
    this->materials[material_id] = material;
    return material;
}

// makes sure all objects have at least one instance
bool Model::add_default_instances()
{
    // apply a default position to all objects not having one
    for (ModelObject *o : this->objects)
        if (o->instances.empty())
            o->add_instance();
    return true;
}

// this returns the bounding box of the *transformed* instances
BoundingBoxf3 Model::bounding_box()
{
    BoundingBoxf3 bb;
    for (ModelObject *o : this->objects)
        bb.merge(o->bounding_box());
    return bb;
}

void Model::center_instances_around_point(const Pointf &point)
{
//    BoundingBoxf3 bb = this->bounding_box();
    BoundingBoxf3 bb;
    for (ModelObject *o : this->objects)
        for (size_t i = 0; i < o->instances.size(); ++ i)
            bb.merge(o->instance_bounding_box(i, false));

    Sizef3 size = bb.size();
    coordf_t shift_x = -bb.min.x + point.x - size.x/2;
    coordf_t shift_y = -bb.min.y + point.y - size.y/2;
    for (ModelObject *o : this->objects) {
        for (ModelInstance *i : o->instances)
            i->offset.translate(shift_x, shift_y);
        o->invalidate_bounding_box();
    }
}

// flattens everything to a single mesh
TriangleMesh Model::mesh() const
{
    TriangleMesh mesh;
    for (const ModelObject *o : this->objects)
        mesh.merge(o->mesh());
    return mesh;
}

static bool _arrange(const Pointfs &sizes, coordf_t dist, const BoundingBoxf* bb, Pointfs &out)
{
    // we supply unscaled data to arrange()
    bool result = Slic3r::Geometry::arrange(
        sizes.size(),               // number of parts
        BoundingBoxf(sizes).max,    // width and height of a single cell
        dist,                       // distance between cells
        bb,                         // bounding box of the area to fill
        out                         // output positions
    );

    if (!result && bb != nullptr) {
        // Try to arrange again ignoring bb
        result = Slic3r::Geometry::arrange(
            sizes.size(),               // number of parts
            BoundingBoxf(sizes).max,    // width and height of a single cell
            dist,                       // distance between cells
            nullptr,                    // bounding box of the area to fill
            out                         // output positions
        );
    }
    
    return result;
}

/*  arrange objects preserving their instance count
    but altering their instance positions */
bool Model::arrange_objects(coordf_t dist, const BoundingBoxf* bb)
{
    // get the (transformed) size of each instance so that we take
    // into account their different transformations when packing
    Pointfs instance_sizes;
    Pointfs instance_centers;
    for (const ModelObject *o : this->objects)
        for (size_t i = 0; i < o->instances.size(); ++ i) {
            // an accurate snug bounding box around the transformed mesh.
            BoundingBoxf3 bbox(o->instance_bounding_box(i, true));
            instance_sizes.push_back(bbox.size());
            instance_centers.push_back(bbox.center());
        }

    Pointfs positions;
    if (! _arrange(instance_sizes, dist, bb, positions))
        return false;
    
	size_t idx = 0;
	for (ModelObject *o : this->objects) {
        for (ModelInstance *i : o->instances) {
            i->offset = positions[idx] - instance_centers[idx];
            ++ idx;
        }
        o->invalidate_bounding_box();
    }
    return true;
}

// Duplicate the entire model preserving instance relative positions.
void Model::duplicate(size_t copies_num, coordf_t dist, const BoundingBoxf* bb)
{
    Pointfs model_sizes(copies_num-1, this->bounding_box().size());
    Pointfs positions;
    if (! _arrange(model_sizes, dist, bb, positions))
        CONFESS("Cannot duplicate part as the resulting objects would not fit on the print bed.\n");
    
    // note that this will leave the object count unaltered
    
    for (ModelObject *o : this->objects) {
        // make a copy of the pointers in order to avoid recursion when appending their copies
        ModelInstancePtrs instances = o->instances;
        for (const ModelInstance *i : instances) {
            for (const Pointf &pos : positions) {
                ModelInstance *instance = o->add_instance(*i);
                instance->offset.translate(pos);
            }
        }
        o->invalidate_bounding_box();
    }
}

/*  this will append more instances to each object
    and then automatically rearrange everything */
void Model::duplicate_objects(size_t copies_num, coordf_t dist, const BoundingBoxf* bb)
{
    for (ModelObject *o : this->objects) {
        // make a copy of the pointers in order to avoid recursion when appending their copies
        ModelInstancePtrs instances = o->instances;
        for (const ModelInstance *i : instances)
            for (size_t k = 2; k <= copies_num; ++ k)
                o->add_instance(*i);
    }
    
    this->arrange_objects(dist, bb);
}

void Model::duplicate_objects_grid(size_t x, size_t y, coordf_t dist)
{
    if (this->objects.size() > 1) throw "Grid duplication is not supported with multiple objects";
    if (this->objects.empty()) throw "No objects!";

    ModelObject* object = this->objects.front();
    object->clear_instances();

    Sizef3 size = object->bounding_box().size();

    for (size_t x_copy = 1; x_copy <= x; ++x_copy) {
        for (size_t y_copy = 1; y_copy <= y; ++y_copy) {
            ModelInstance* instance = object->add_instance();
            instance->offset.x = (size.x + dist) * (x_copy-1);
            instance->offset.y = (size.y + dist) * (y_copy-1);
        }
    }
}

ModelObject::ModelObject(Model *model, const ModelObject &other, bool copy_volumes) :  
    name(other.name),
    input_file(other.input_file),
    instances(),
    volumes(),
    config(other.config),
    layer_height_ranges(other.layer_height_ranges),
    layer_height_profile(other.layer_height_profile),
    layer_height_profile_valid(other.layer_height_profile_valid),
    origin_translation(other.origin_translation),
    m_bounding_box(other.m_bounding_box),
    m_bounding_box_valid(other.m_bounding_box_valid),
    m_model(model)
{
    if (copy_volumes) {
        this->volumes.reserve(other.volumes.size());
        for (ModelVolumePtrs::const_iterator i = other.volumes.begin(); i != other.volumes.end(); ++i)
            this->add_volume(**i);
    }
    
    this->instances.reserve(other.instances.size());
    for (ModelInstancePtrs::const_iterator i = other.instances.begin(); i != other.instances.end(); ++i)
        this->add_instance(**i);
}

ModelObject& ModelObject::operator=(ModelObject other)
{
    this->swap(other);
    return *this;
}

void ModelObject::swap(ModelObject &other)
{
    std::swap(this->input_file,             other.input_file);
    std::swap(this->instances,              other.instances);
    std::swap(this->volumes,                other.volumes);
    std::swap(this->config,                 other.config);
    std::swap(this->layer_height_ranges,    other.layer_height_ranges);
    std::swap(this->layer_height_profile,   other.layer_height_profile);
    std::swap(this->layer_height_profile_valid,    other.layer_height_profile_valid);
    std::swap(this->origin_translation,     other.origin_translation);
    std::swap(m_bounding_box,               other.m_bounding_box);
    std::swap(m_bounding_box_valid,         other.m_bounding_box_valid);
}

ModelObject::~ModelObject()
{
    this->clear_volumes();
    this->clear_instances();
}

ModelVolume* ModelObject::add_volume(const TriangleMesh &mesh)
{
    ModelVolume* v = new ModelVolume(this, mesh);
    this->volumes.push_back(v);
    this->invalidate_bounding_box();
    return v;
}

ModelVolume* ModelObject::add_volume(TriangleMesh &&mesh)
{
    ModelVolume* v = new ModelVolume(this, std::move(mesh));
    this->volumes.push_back(v);
    this->invalidate_bounding_box();
    return v;
}

ModelVolume* ModelObject::add_volume(const ModelVolume &other)
{
    ModelVolume* v = new ModelVolume(this, other);
    this->volumes.push_back(v);
    this->invalidate_bounding_box();
    return v;
}

void ModelObject::delete_volume(size_t idx)
{
    ModelVolumePtrs::iterator i = this->volumes.begin() + idx;
    delete *i;
    this->volumes.erase(i);
    this->invalidate_bounding_box();
}

void ModelObject::clear_volumes()
{
    for (ModelVolume *v : this->volumes)
        delete v;
    this->volumes.clear();
    this->invalidate_bounding_box();
}

ModelInstance* ModelObject::add_instance()
{
    ModelInstance* i = new ModelInstance(this);
    this->instances.push_back(i);
    this->invalidate_bounding_box();
    return i;
}

ModelInstance* ModelObject::add_instance(const ModelInstance &other)
{
    ModelInstance* i = new ModelInstance(this, other);
    this->instances.push_back(i);
    this->invalidate_bounding_box();
    return i;
}

void ModelObject::delete_instance(size_t idx)
{
    ModelInstancePtrs::iterator i = this->instances.begin() + idx;
    delete *i;
    this->instances.erase(i);
    this->invalidate_bounding_box();
}

void ModelObject::delete_last_instance()
{
    this->delete_instance(this->instances.size() - 1);
}

void ModelObject::clear_instances()
{
    for (ModelInstance *i : this->instances)
        delete i;
    this->instances.clear();
    this->invalidate_bounding_box();
}

// Returns the bounding box of the transformed instances.
// This bounding box is approximate and not snug.
BoundingBoxf3 ModelObject::bounding_box()
{
    if (! m_bounding_box_valid) {
        BoundingBoxf3 raw_bbox;
        for (const ModelVolume *v : this->volumes)
            if (! v->modifier)
                raw_bbox.merge(v->mesh.bounding_box());
        BoundingBoxf3 bb;
        for (const ModelInstance *i : this->instances)
            bb.merge(i->transform_bounding_box(raw_bbox));
        m_bounding_box = bb;
        m_bounding_box_valid = true;
    }
    return m_bounding_box;
}

// A mesh containing all transformed instances of this object.
TriangleMesh ModelObject::mesh() const
{
    TriangleMesh mesh;
    TriangleMesh raw_mesh = this->raw_mesh();
    for (const ModelInstance *i : this->instances) {
        TriangleMesh m = raw_mesh;
        i->transform_mesh(&m);
        mesh.merge(m);
    }
    return mesh;
}

// Non-transformed (non-rotated, non-scaled, non-translated) sum of non-modifier object volumes.
// Currently used by ModelObject::mesh(), to calculate the 2D envelope for 2D platter
// and to display the object statistics at ModelObject::print_info().
TriangleMesh ModelObject::raw_mesh() const
{
    TriangleMesh mesh;
    for (const ModelVolume *v : this->volumes)
        if (! v->modifier)
            mesh.merge(v->mesh);
    return mesh;
}

// 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.
BoundingBoxf3 ModelObject::raw_bounding_box() const
{
    BoundingBoxf3 bb;
    for (const ModelVolume *v : this->volumes)
        if (! v->modifier) {
            if (this->instances.empty()) CONFESS("Can't call raw_bounding_box() with no instances");
            bb.merge(this->instances.front()->transform_mesh_bounding_box(&v->mesh, true));
        }
    return bb;
}

// This returns an accurate snug bounding box of the transformed object instance, without the translation applied.
BoundingBoxf3 ModelObject::instance_bounding_box(size_t instance_idx, bool dont_translate) const
{
    BoundingBoxf3 bb;
    for (ModelVolume *v : this->volumes)
        if (! v->modifier)
            bb.merge(this->instances[instance_idx]->transform_mesh_bounding_box(&v->mesh, dont_translate));
    return bb;
}

void ModelObject::center_around_origin()
{
    // calculate the displacements needed to 
    // center this object around the origin
	BoundingBoxf3 bb;
	for (ModelVolume *v : this->volumes)
        if (! v->modifier)
			bb.merge(v->mesh.bounding_box());
    
    // first align to origin on XYZ
    Vectorf3 vector(-bb.min.x, -bb.min.y, -bb.min.z);
    
    // then center it on XY
    Sizef3 size = bb.size();
    vector.x -= size.x/2;
    vector.y -= size.y/2;
    
    this->translate(vector);
    this->origin_translation.translate(vector);
    
    if (!this->instances.empty()) {
        for (ModelInstance *i : this->instances) {
            // apply rotation and scaling to vector as well before translating instance,
            // in order to leave final position unaltered
            Vectorf3 v = vector.negative();
            v.rotate(i->rotation);
            v.scale(i->scaling_factor);
            i->offset.translate(v.x, v.y);
        }
        this->invalidate_bounding_box();
    }
}

void ModelObject::translate(coordf_t x, coordf_t y, coordf_t z)
{
    for (ModelVolume *v : this->volumes)
        v->mesh.translate(float(x), float(y), float(z));
    if (m_bounding_box_valid) 
        m_bounding_box.translate(x, y, z);
}

void ModelObject::scale(const Pointf3 &versor)
{
    for (ModelVolume *v : this->volumes)
        v->mesh.scale(versor);
    // reset origin translation since it doesn't make sense anymore
    this->origin_translation = Pointf3(0,0,0);
    this->invalidate_bounding_box();
}

void ModelObject::rotate(float angle, const Axis &axis)
{
    for (ModelVolume *v : this->volumes)
        v->mesh.rotate(angle, axis);
    this->origin_translation = Pointf3(0,0,0);
    this->invalidate_bounding_box();
}

void ModelObject::mirror(const Axis &axis)
{
    for (ModelVolume *v : this->volumes)
        v->mesh.mirror(axis);
    this->origin_translation = Pointf3(0,0,0);
    this->invalidate_bounding_box();
}

size_t ModelObject::materials_count() const
{
    std::set<t_model_material_id> material_ids;
    for (const ModelVolume *v : this->volumes)
        material_ids.insert(v->material_id());
    return material_ids.size();
}

size_t ModelObject::facets_count() const
{
    size_t num = 0;
    for (const ModelVolume *v : this->volumes)
        if (! v->modifier)
            num += v->mesh.stl.stats.number_of_facets;
    return num;
}

bool ModelObject::needed_repair() const
{
    for (const ModelVolume *v : this->volumes)
        if (! v->modifier && v->mesh.needed_repair())
            return true;
    return false;
}

void ModelObject::cut(coordf_t z, Model* model) const
{
    // clone this one to duplicate instances, materials etc.
    ModelObject* upper = model->add_object(*this);
    ModelObject* lower = model->add_object(*this);
    upper->clear_volumes();
    lower->clear_volumes();
    upper->input_file = "";
    lower->input_file = "";
    
    for (ModelVolume *volume : this->volumes) {
        if (volume->modifier) {
            // don't cut modifiers
            upper->add_volume(*volume);
            lower->add_volume(*volume);
        } else {
            TriangleMesh upper_mesh, lower_mesh;
            // TODO: shouldn't we use object bounding box instead of per-volume bb?
            coordf_t cut_z = z + volume->mesh.bounding_box().min.z;
            if (false) {
//            if (volume->mesh.has_multiple_patches()) {
                // Cutting algorithm does not work on intersecting meshes.
                // As we are not sure whether the meshes don't intersect,
                // we rather split the mesh into multiple non-intersecting pieces.
                TriangleMeshPtrs meshptrs = volume->mesh.split();
                for (TriangleMeshPtrs::iterator mesh = meshptrs.begin(); mesh != meshptrs.end(); ++mesh) {
                    printf("Cutting mesh patch %d of %d\n", size_t(mesh - meshptrs.begin()));
                    (*mesh)->repair();
                    TriangleMeshSlicer tms(*mesh);
                    if (mesh == meshptrs.begin()) {
                        tms.cut(cut_z, &upper_mesh, &lower_mesh);
                    } else {
                        TriangleMesh upper_mesh_this, lower_mesh_this;
                        tms.cut(cut_z, &upper_mesh_this, &lower_mesh_this);
                        upper_mesh.merge(upper_mesh_this);
                        lower_mesh.merge(lower_mesh_this);
                    }
                    delete *mesh;
                }
            } else {
                printf("Cutting mesh patch\n");
                TriangleMeshSlicer tms(&volume->mesh);
                tms.cut(cut_z, &upper_mesh, &lower_mesh);
            }

            upper_mesh.repair();
            lower_mesh.repair();
            upper_mesh.reset_repair_stats();
            lower_mesh.reset_repair_stats();
            
            if (upper_mesh.facets_count() > 0) {
                ModelVolume* vol    = upper->add_volume(upper_mesh);
                vol->name           = volume->name;
                vol->config         = volume->config;
                vol->set_material(volume->material_id(), *volume->material());
            }
            if (lower_mesh.facets_count() > 0) {
                ModelVolume* vol    = lower->add_volume(lower_mesh);
                vol->name           = volume->name;
                vol->config         = volume->config;
                vol->set_material(volume->material_id(), *volume->material());
            }
        }
    }
}

void ModelObject::split(ModelObjectPtrs* new_objects)
{
    if (this->volumes.size() > 1) {
        // We can't split meshes if there's more than one volume, because
        // we can't group the resulting meshes by object afterwards
        new_objects->push_back(this);
        return;
    }
    
    ModelVolume* volume = this->volumes.front();
    TriangleMeshPtrs meshptrs = volume->mesh.split();
    for (TriangleMesh *mesh : meshptrs) {
        // Snap the mesh to Z=0.
        float z0 = FLT_MAX;
        
        mesh->repair();
        
        ModelObject* new_object = m_model->add_object(*this, false);
        new_object->input_file  = "";
        ModelVolume* new_volume = new_object->add_volume(*mesh);
        new_volume->name        = volume->name;
        new_volume->config      = volume->config;
        new_volume->modifier    = volume->modifier;
        new_volume->material_id(volume->material_id());
        
        new_objects->push_back(new_object);
        delete mesh;
    }
    
    return;
}

void ModelVolume::material_id(t_model_material_id material_id)
{
    this->_material_id = material_id;
    
    // ensure this->_material_id references an existing material
    (void)this->object->get_model()->add_material(material_id);
}

ModelMaterial* ModelVolume::material() const
{ 
    return this->object->get_model()->get_material(this->_material_id);
}

void ModelVolume::set_material(t_model_material_id material_id, const ModelMaterial &material)
{
    this->_material_id = material_id;
    (void)this->object->get_model()->add_material(material_id, material);
}

ModelMaterial* ModelVolume::assign_unique_material()
{
    Model* model = this->get_object()->get_model();
    
    // as material-id "0" is reserved by the AMF spec we start from 1
    this->_material_id = 1 + model->materials.size();  // watchout for implicit cast
    return model->add_material(this->_material_id);
}

// Split this volume, append the result to the object owning this volume.
// Return the number of volumes created from this one.
// This is useful to assign different materials to different volumes of an object.
size_t ModelVolume::split()
{
    TriangleMeshPtrs meshptrs = this->mesh.split();
    if (meshptrs.size() <= 1) {
        delete meshptrs.front();
        return 1;
    }

    size_t idx = 0;
    size_t ivolume = std::find(this->object->volumes.begin(), this->object->volumes.end(), this) - this->object->volumes.begin();
    std::string name = this->name;
    for (TriangleMesh *mesh : meshptrs) {
        mesh->repair();
        if (idx == 0)
            this->mesh = std::move(*mesh);
        else
            this->object->volumes.insert(this->object->volumes.begin() + (++ ivolume), new ModelVolume(object, *this, std::move(*mesh)));
        char str_idx[64];
        sprintf(str_idx, "_%d", idx + 1);
        this->object->volumes[ivolume]->name = name + str_idx;
        delete mesh;
        ++ idx;
    }
    
    return idx;
}

void ModelInstance::transform_mesh(TriangleMesh* mesh, bool dont_translate) const
{
    mesh->rotate_z(this->rotation);                 // rotate around mesh origin
    mesh->scale(this->scaling_factor);              // scale around mesh origin
    if (!dont_translate)
        mesh->translate(this->offset.x, this->offset.y, 0);
}

BoundingBoxf3 ModelInstance::transform_mesh_bounding_box(const TriangleMesh* mesh, bool dont_translate) const
{
    // Rotate around mesh origin.
    double c = cos(this->rotation);
    double s = sin(this->rotation);
    BoundingBoxf3 bbox;
    for (int i = 0; i < mesh->stl.stats.number_of_facets; ++ i) {
        const stl_facet &facet = mesh->stl.facet_start[i];
        for (int j = 0; j < 3; ++ j) {
            stl_vertex v = facet.vertex[j];
            double xold = v.x;
            double yold = v.y;
            v.x = float(c * xold - s * yold);
            v.y = float(s * xold + c * yold);
            bbox.merge(Pointf3(v.x, v.y, v.z));
        }
    }
    if (! empty(bbox)) {
        // Scale the bounding box uniformly.
        if (std::abs(this->scaling_factor - 1.) > EPSILON) {
            bbox.min.x *= float(this->scaling_factor);
            bbox.min.y *= float(this->scaling_factor);
            bbox.min.z *= float(this->scaling_factor);
            bbox.max.x *= float(this->scaling_factor);
            bbox.max.y *= float(this->scaling_factor);
            bbox.max.z *= float(this->scaling_factor);
        }
        // Translate the bounding box.
        if (! dont_translate) {
            bbox.min.x += float(this->offset.x);
            bbox.min.y += float(this->offset.y);
            bbox.max.x += float(this->offset.x);
            bbox.max.y += float(this->offset.y);
        }
    }
    return bbox;
}

BoundingBoxf3 ModelInstance::transform_bounding_box(const BoundingBoxf3 &bbox, bool dont_translate) const
{
    // rotate around mesh origin
    double c = cos(this->rotation);
    double s = sin(this->rotation);
    Pointf3 pts[4] = {
        bbox.min,
        bbox.max,
        Pointf3(bbox.min.x, bbox.max.y, bbox.min.z),
        Pointf3(bbox.max.x, bbox.min.y, bbox.max.z)
    };
    BoundingBoxf3 out;
    for (int i = 0; i < 4; ++ i) {
        Pointf3 &v = pts[i];
        double xold = v.x;
        double yold = v.y;
        v.x = float(c * xold - s * yold);
        v.y = float(s * xold + c * yold);
        v.x *= this->scaling_factor;
        v.y *= this->scaling_factor;
        v.z *= this->scaling_factor;
        if (! dont_translate) {
            v.x += this->offset.x;
            v.y += this->offset.y;
        }
        out.merge(v);
    }
    return out;
}

void ModelInstance::transform_polygon(Polygon* polygon) const
{
    polygon->rotate(this->rotation);                // rotate around polygon origin
    polygon->scale(this->scaling_factor);           // scale around polygon origin
}

}